I going to assume that this an XP machine so I will list the instructions for this first. I also left the same response in the laptops forum.
Ok this is what you are going to do.
Go into your BIOS and adjust the boot configuration so the machine will boot from the CD ROM. Before executing the setting save and allowing the machine to reboot, insert your Windows XP installation CD into the drive.
Now the machine will run through the BIOS, and then the computer will skip the bootstrap program aka NTLDR and boot directly from the CD.
When you get to the main menu of the Windows Installation CD press "R" to enter the Windows Recovery Console. I am going to provide lind of patronozong instructions because I don't know if you have any experiance in the RC. Allow the RC to go through the process of starting, you will be able to see the status at the bottom of the screen. In the status area it will first want you to press any key if you are using a non US standard keyboard. There will be a countdown next to this, let that finish and do not press any keys.
Now move your attention from the status bar to the main screen. The RC now wants you to select what Windows installation you want it to initiate for repairs. If you have a dual boot system more then one selection will be tlisted, by defualt the C: drive is always put as the first selection on the list. If this is the location of your Windows installation press "1" and then hit enter.
Now the RC is going to ask you to input your admin password, do so and press enter, you get three tries to enter the correct password, if you fail to do so the RC will lock you out and restart the system in which case you will have to wait for the install console to reinitiate and then reneter the RC, and redo every step we went through thus far.
Once you enter your admin password the console will bring you to a prompt similar to that in DOS. Now again I don't know if you have ever used DOS before so bare with me if you have. DOS is a completely command line based interface so you will be typing out commands for the PC to execute.
So now we are at the prompt which should read C: or C:\Windows, either will do. Now you are going to type the following command
at the prompt type the following command exactly:
this is very important I used the D: drive in my example I am assuming this is your CD ROM drive if it is not, please replace the letter D with the correct letter, the same goes for C:, if this is not the correct drive for your Windows Hard Drive please make the proper corrections. Also make sure to place a space between com and C. Once you typed the command hit enter.
Thats it you hopefully just fixed your pc. (If you did not which we will find out later then you have another problem)When the prompt returns that means the command executed successfully. What you just did was replace a file called ntdetect.com it is a registry file that is one of the first files to be executed by the NTLDR, the Windows Bootstrap program. What this file does is collect data from the computers BIOS during boot up. And then the file passes this data to the actual Windows kernel (the core of Windows).
At the prompt type the word exit and hit enter. This will restart the computer. Once again go into the BIOS and reset the boot configuration so that the PC boots from the hard drive. Remove the CD and save the settings the computer will reboot and now you should go directly into Windows.
Again I apologize if this seemed a little patronizing I don't know the extent of your computer skills. Also these are directions for an XP machine only. If you have 2000, please let me know I will post the directions. If you have any questions or trouble please post them and I will try to get back to you as soon as I can. Finally let me know how it turns out. Good Luck