I recommend leaving .dll and other system files alone UNLESS a reputable program identifies them as a problem.(Such as antivirus or spyware remover.)
Windows XP does have a program called "System File Checker" which will find corrupted or damaged system files, but it's better left for situations when you think you have a problem with computer operations.
Description of Windows XP and Windows Server 2003 System File Checker (Sfc.exe)
I find it sufficient to routinely use the tools you have mentioned, "harden" my browser so malware finds it difficult to get on the machine, keep current with all security updates, and do a lot of research about the newest exploits.
Hope this helps.
I noticed that too often viruses etc. attack
(add to/change) your DLL files.
Is there a special tool or web site to help determine
which DLL files are good and which are viruses/adware, etc.? I right click some to check the properties, but not all of them give me any useful info. If there are harmful ones there taking up space, I'd like to be able
to remove them safely.
P.S., I have XP and all the necessary anti-virus/spyware/adware tools updated. Thanks for
any help. Becca