Reply #11: Here's what I would do

[48pan]

Start in safe mode
If necessary log in with administrator privelige
Run your virus checker (it is up-to-date isn't it?)
It that works, get Adaware SE and run that.

There a several worm/trojan programs out there right now that are downright rude. There are even a couple that will eat your BIOS EPROM chip. You may have one that eats operating system files.

If it won't start in safe mode, start from a CD with the WinXP disk. Reinstall/repair the operating system and try the same thing.

If it won't boot from the CD, you probably have hardware problems. Seek professional help in that case.

Worst case without broken hardware, you will have to reformat the hard disk and recover the system with your original CD's.

Make sure to update WinXP as soon as it is up and running. I strongly recommend downloading and using Firefox as your browser. For the time being, it seems to be immune to worms and trojans plus adware/malware/spyware.