OK. Is the account you are running from the only one that is set up? If so, can you go to the Control Panel | Users and set up a user-level account. Reboot and see what happens when you attempt any of the stuff from previous posts.
If you still have no luck, put the W2K CD in and then go to Start|Run and type in sfc /scannow and hit the OK button. See how it goes after that. Do not omit the space between the sfc and the / switch.
Let us know.