The easiest way to fix this is to back up all your data files, do a clean install of XP SP2, stick all the MS updates on it and start over. The cause could be a myriad of things(e.g. it's possible you've been got by some malware).
Make sure your virus detection rules, spyware scanners(I use MS Antispyware and Spybot, but there are others) are up to date with the latest versions BEFORE connecting to web sites etc. on the Net.
You might want to take advantage of the free scans at:
when you have your Internet connection set up.
Make sure to do a hard format when you reinstall XP - this will pick up any disk errors(it may be that the HD is failing, in which case the data backup is even more important.
I'd make sure System Restore is turned on and that you take a restore point before connecting, getting mail set up, reinstalling applications etc.
If you've got your data on CD/DVD whatever, it would be a good idea to run a full virus scan on it before copying it back(you don't want to reintroduce problems). Speaking for myself, I find I tend to do this every 12-18 months - Windows just seems to slow down over time as the amount of data on the system increases.
This may sound like a lot of work, but it's surprising how long you can take trying various things that may be the root cause. This way, you know that your side of the street is clean!
Submitted by: Rick S.
rundll32.exe is a process which executes DLL's an places their libraries into the memory, so they can be used more efficiently by applications.This program is important for the stable and secure running of your computer and should not be terminated.
Note: rundll32.exe is also a process which is registered as the W32.Miroot.Worm. This Trojan allows attackers to access your computer, stealing passwords and personal data. It is a registered security risk and should be removed immediately. Please see additional details regarding this process
Suggestion that your antivirus program is removing this dll. You will need to restore from original CD. Also suggest that you protect yourself with a firewall and to make sure your antivirus software definition files stay updated. Also some comprehensive spyware removal program. You should also ensure that your computer is configured to receive and install the monthly security patches from microsoft. I would highly recommend the symantec package called ??Internet Security 2005?? It has a firewall, norton antivirus which also removes spyware and some other security features to protect your machine viruses, spyware, adware, malware and hackers. This is the first rule in connecting a PC to the internet. Also...you should never open any email from unknown senders and be aware of phishing.
Assuming that the windows OS on your PC was installed in a folder called Windows, the normal location of this missing file (rundll32.exe) is..
If you were infected with the miroot worm, it would have overwritten this microsoft file with its own version. Your antivirus software may remove this file when it scans your hard drive leaving you with no file at all. You need to make sure that your antivirus software is always updated and that real time scan is turned on. Your virus definition file within your antivirus software should never be older than 7 days.
Info on this miroot virus...
Hope this helps some...
Submitted by: Valentin P.
I have a solution for your problem here sir.
The first step is to get another copy of it off of the web. You can do this by clicking on this link http://p-nand-q.com/download/tools/rundll32.zip and saving the file to somewhere u know where to get to it.
After u do that then you have to go to the START--->SEARCH--->FOR FILES OR FOLDERS--->All Files and Folders and then in the All or Part of the File Name box you type ??rundll32.dll?? and make sure your searching in all folders possible (check the More Advanced Options and make sure the first three things are checked). Then start your search. After a minute or two this should bring up the file rundll32.dll and the directory you have to go to should be right next to it.
The location of rundll32.dll should look similar to this, but not necessarily the same---C:/windows/system32-- now if you need to copy that location down on a piece of paper then you should do so.
Now go to where u saved that file we just downloaded a few minutes ago. Double Click and open it, Now somewhere in this process it should say ??Directory to Extract to:?? and in the box below that you type what you wrote down earlier. Then click Next and the file should extract into that file, and if you get a message saying ??Are you sure you want to overwrite this file??? and then you should click yes. After that is done, uncheck the box that has now appeared and then hit the Done or Finished button.
After you have finished that you should have no more problems with that file at all. Best of luck with the process and i hope the description was detailed enough for you to understand.
Submitted by: Blake
First off - an explanation of what RunDLL32.exe is. It's a system program, located in C:\Winnt\System32 in NT-based systems (like yours) where C: is the Windows drive. It is used to run DLL files, files that essentially contain libraries of system commands. Usually it is used by Microsoft, to set options in Windows, but it can be used -- or mis-used -- by others.
It's unlikely - if not impossible - that you could do anything in Windows without the file, so I doubt you're missing it. You can check for the file in your windows system32 directory if you like; but you probably couldn't start up windows without it. If it's missing, a system repair - accomplished by booting your computer with the XP disk in the CD drive - would fix that. However, it sounds like your repair folks have done that already.
What's a lot more likely to be the culprit -- are the email attachments you mention.
Not many email attachments have any reason to be using rundll32.exe.
However, there is one major type of attachment that uses it.
Yep, you guessed it. A virus. Viruses use rundll32.exe often, to allow them to run their malicious code - to change system files, to find system information (such as e-mail addresses), etc.
Make sure these e-mail attachments you are talking about are valid, and useful, and worth running. Make sure they're not viruses, by scanning with an up-to-date, thorough virus scanner. Also, scan your system -- one tactic viruses use, is to replace rundll32.exe with their own version, which of course contains something malicious in it.
Thanks, and good luck!!
Submitted by: Joe M. of Chicago
Hello Allen O.
Your question was (basically) ??What is rundll32.exe and how can I fix it because it's gone or corrupt?? and you are running Windows XP.
My first suggestion is that you check your system for viruses. If you do not have virus protection, please let me "highly" recommend Computer Associates eTrust AntiVirus (http://www3.ca.com/Solutions/Product.asp?ID=156). I've used it for over 5 years and have NEVER had a virus (knock on wood I recommend it to all of my clients (I work on computers and am a web developer).
To answer your question, I went right to the source(es)...
What is rundll32.exe? from Microsoft ( http://www.microsoft.com )... ??Rundll32 loads and runs 32-bit DLLs.??
Where is it... you can't find it or it won't work because it may be corrupted?... from ??I Am Not A Geek?? (http://www.iamnotageek.com/a/rundll32.exe.php) (--- ??Virus Precaution: The original file from Microsoft gets placed in the location at C:\WINDOWS\System32\rundll32.exe . If you find it anywhere else then you should be suspicious...??
Just so you know, Allen, some ??malware?? applications try to pose as valid applications and thus use run32dll.exe. Some examples are W32.Miroot.Worm, Backdoor.Lastdoor, Trojan.StartPage, among others...
So, Allen, how do you fix it? Again, the answer comes from Microsoft...
The advice from Microsoft (http://support.microsoft.com/default.aspx?scid=kb;en-us;812340 ).
CAUSE: This issue occurs because of a missing or corrupted Rundll32.exe file. This issue may also be caused by a virus.
RESOLUTION: To resolve this issue, follow these steps:
1. Put the Windows XP CD ROM disk in the CD ROM drive.
2. Click Start, and then click Run.
3. Type expand X:\i386\rundll32.ex_ c:\windows\rundll32.exe in the Open box, where X is the letter of your CD ROM Drive.
4. Restart the computer.
Submitted by: Sandy H.
Allen, I am sorry to tell you that you've lost a key Windows service. RunDll32.exe is a program that converts dynamic link library files (.dll) into executable programs (.exe). The difference between the two are as follows: programs are usually run independently of any other programs, that is, they do not need another application to function. Dll files on the other hand are a sort of sub-program (technically, an application extension) and the parent program contains the instruction required to decode and use the information contained in them.
The RunDll32 program removes that requirement and allows parts of a program to be run without actually having to load the entire program. This is to reduce memory usage (as one part of a program will obviously require less of the memory than the entire program) and to reduce strain on the CPU. As an analogy, let's take the problem you presented in your question: you say RunDll32.exe is required to view attachments sent to you through e-mail. Since you did not specify what type of file these attachments were (pictures, movies, documents, etc.) I will use pictures in this scenario. As you can see, you are able to view your received e-mails through either your browser or an e-mail client such as Outlook (Express), Eudora, or what have you. No matter what method you use, you are viewing the e-mail through a parent program. But when you try to view the attachments (in my example, pictures) you receive the error message and nothing productive happens, ideally, you get to view the pictures. This is because the Picture Viewer is a sub-app of Windows and since RunDll32 is missing, Windows cannot load the it as it is encoded in a .dll file. To XP, the Picture Viewer dll file is nothing more than a series of meaningless characters jumbled together.
But enough background. I assume you care more about how to remedy the situation. Before carrying out any instructions, you will want to print this document. I did not try to print when I had this problem, so I do not know if the Print function even works. If not, e-mail this to a geographically close computer where you can print. I assume you care more about how to remedy the situation. I regret to tell you the solution is not an easy or friendly one. I had the same problem myself and believe me I tried every conceivable solution to no avail. Finally, I realized that the only thing left to do was to format the hard drive. (Gasp!) Now, this is not as difficult a task as it is made out to be. In fact, losing this file is not all bad because now you can start fresh with your computer free of spyware, viruses, etc... Follow this checklist before attempting any major system changes.
 Gather together in one folder all documents, pictures, personal files, etc. This will be your transfer folder. If it is not already there, move it to the desktop by right-clicking on it and selecting Cut. Now go to the desktop and right-click in an empty space and choose Paste. Now I assume you have lost CD burning capabilities (you DO have a CD burner, right?) so I suggest either e-mailing this folder to yourself as an attachment, or obtaining a free online storage account. (I use http://www.streamload.com; otherwise search for free online storage.) Bottom line, get a copy of that folder off your computer.
 Hunt through your house to locate as many installation CDs as possible. When you format, all programs will be lost to the big hard drive in the sky. I suggest going into Start -> Control Panel -> Add/Remove Programs and find the installation media for each.
 Locate your Microsoft XP CD Key. It should be attached to the body of your computer, but if you're like me, it's lost somewhere in the closet. If you cannot find it, you can call the Microsoft product activation center - just explain that you had to format the drive and Windows is NOT being installed on more than one computer.
 Patience. Do not get frustrated with the machine. This is the most valuable tip anyone can give about computers. Just take each block one step at a time.
*** FORMATTING ***
To begin formatting, insert the Windows XP CD in the drive tray. After ensuring that all personal data is in some way backed up, restart the computer. The screen should progress to this line: Press Enter to boot from CD, or something to that extent. Press Enter and wait. If you get this far, ignore the next paragraph.
NOTE: if you do not get that line, watch for some key place to enter the System BIOS which control the bare essentials and workings of the computer. After restarting, it should say something like Press Del to enter Setup. Press Del and use your cursor arrows to navigate to the different menus. You are looking for something that says Boot Sequence. When you find it, assign A: Floppy as 1st Boot Device, CD-ROM as 2nd, and Hard Drive (IDE-0) as 3rd. Now save changes and restart. Remember, do not modify any other values in the BIOS settings. Doing so could seriously hurt the system. Repeat Step 1 above.
Now, at this blue screen, you have a few choices to make. Read each screen carefully (except for the disclaimer, just press F8) and look for key buttons to press. I believe you want to look for either Delete Partition or Install Windows XP. Press the corresponding key. A warning screen will ask if you really want to delete the partition. Press L. (But only if you REALLY want to. I stress that after you press L, ALL data is lost) After you have deleted the partition, create a new one and choose Install XP on C: Partition (Drive Space) After a few more screens, file copying begins. The computer will restart, and then Setup will commence. From this point on, most screens are user-friendly.
Ok, so Windows is installed and more or less in working order. Firstly, install any missing drivers such as sound, video, ethernet, etc... These should be located on your motherboard CD. Next, install all your programs. Now, retrieve those personal files from the internet or e-mail. If you chose e-mail, you will need to reconfigure your POP settings. Just remember, the mail server is POP3, the incoming mail (POP3) value is pop, the outgoing mail (SMTP) value is smtp. From here on in, your on your own.
Hope this helped.
Submitted by: Chris B.