Just because you ran an antivirus program doesn't mean it is a bit of spyware or malware. Do you have an alternative spyware detection program?
Also, you should boot up into safe mood and run msconfig to see what programs start to run when you turn on the computer. Turn off the programs you don't want to start when the computer boots up. Perhaps one of these programs have a glitch or a bug in them. I used to use the BOINC program so I could run the [email protected]
program at home. Then several months ago, my computer started to crash minutes after I booted my laptop. When I ran msconfig I then turned off BOINC from turning on at startup.
From then on, my computer hasn't crashed. Sadly, I had to delete the program and even when I redownloaded it, I had the same crashing problem so I guess I can't run it on this computer anymore (or until I can figure where's the conflict between my Dell, Vista, and BOINC).
It could also be a problem/glitch in your registry. Something like the latest version of Registry Mechanic or perhaps iolo System Mechanic. Registry Mechanic strictly focuses on the registry while System Mechanic is an all around diagnostic and maintenance based program.