EXPLORER.EXE corrupted or infected

Hello,
Desktop is dropping after boot. I cannot open task manager because I try but I get error message that says task manager was disabled by administrator. I have to click ok. Then I get the same problem. I cannot do a system restore because I cannot go back past the last time I tried to do it, which was two days ago. There are no more available days to restore to.
Symptoms: When I boot my pc, it comes up fine, with all the regular icons on the desktop and programs appear to be running, but then my desktop icons, and all files I might be trying to click on close down in a flash. Then they re-apear again, just to do it all over again. I managed to get to the run function to run regedit. That's as far as I want to go because I don't know where to go in regedit to find the culpret infected file to delete it. I try to run virus scan with Mcaffee, but nothing is found.
Question: Is there anywhere that I might look to find the culpret file in the regedit editor? From what I have managed to find on the Net, it involves the explorer.exe file and I don't know what to do to get to this infection, and I do not, under any circumstances, want to re-install my OS just to get rid of it. I have no back-up for all my files, I know I am a fool for not backing up my files daily, but what is done is done. Can I fix this? The pc is rendered useless without the fix or re-install. Can't I just find the infected file, delete it, and then re-establish my explorer.exe file at re-boot from the install disk or the Internet?
Question: Where is the explorer.exe file located in the registry? Can this issue be resolved without drastic measures? Please help me. All my files from over 14 classes are on that drive, and if I lose them, I have nothing to refer to for my capstone project for graduation BaSc Degree in four months. I don't know where else to turn except the Internet and you.
Thank you. DennisPS