Could be some virus has infected a driver. Any strange reports from your Norton Semantec or similar security program?
Agreed. Image.dll?
If you can get into the operating system desktop some of the time, go to Start-- Run-- type MSCONFiG-- go to the rightmost tab, marked Startup, uncheck everything, and see if your system boots normally.
Then update your virus definitions on whatever antivirus program that you have, and run a full scan.