I would start with restoring the registry. Press alt+f4 on this nice empty desktop you've got, and choose to reboot in MS-DOS. Then type scanreg /restore (end command with enter) and choose a date when everything was still OK.
Then scan your system for malware with all the tools mentioned by Grif Thomas in http://reviews.cnet.com/5208-6121-0.html?forumID=45&threadID=24325&messageID=581353&tag=
Hope this helps.
I lost all the icons on the display screen & I can't see the start button. Can somebody tell me what to do about getting the icons back?