The corrupt desktop is usually one of two things:
You’ve corrupted your computer profile, i.e. the things that make the computer think you are YOU.
I’d copy your data off the machine, right away.
If you go to My Computer, and right-click on your C drive, choose the option for Properties. This opens up another box. Choose the tab for Tools, and go to the Error-Checking option. Click the check-now box, and choose both options. You’ll have to reboot, and it’ll check your disk again. See what happens.
If your profile is corrupt, go and create another user on the computer. If that profile has no issues, copy your data over to it, and just log in as that person.
Hopefully, you’ve got some good anti-virus checking software on there. Scan the sucker to an inch of its life, and verify you’re clean.
All in all - Start considering a new hard drive.