I have a one year old Win Vista PC, that came with Windows Defender, and I added on Trend Micro Antivirus. Everything has been working fine, along with the 3 additional freeware spy/malware programs that I installed:Malware bytes, Ad-Aware, and Spybot search and destroy. I picked a 'Win32.zafi.B' worm somewhere, and none of my programs(with updated programs and definitions) was able to find it. After a bit of research, I bought 'Spyware Doctor with Anti-virus', as it's promotional material said it would find and eliminate any worms. I installed it, ran the full scan, and it found a few 'bugs', but not the one mentioned above. I sent an email to PCTools, where I bought it from concerning this, and have yet to hear back from them...it's been a week. In the meantime, my Windows Defender would display a pop up window every few hours saying that I have two anti-virus programs running, and if I wanted to disable Defender. I said 'no', as I thought that two would be better than one. After a day of pop ups, I had my first BSOD error 'Driver IRQL not less or equal'. I didn't know what this meant, or that it was in relation to my newly installed Spyware Doctor. I did a system restore to a point in time to just before I installed Spyware Doctor. At this point, Windows Defender is running, and there is no Spyware Doctor running. 3 days go by and no BSOD's. At this point I decided to try an experiment...I turned off Defender, and re-installed Spyware Doctor, thinking that the BSOD was due to a conflict between these two programs. My PC wasn't up more than a few hours before it crashed again. I did another system restore, and now I'm back to where I was before buying Spyware Doctor-3 days and no BSOD's. So, it looks as if my PC just doesn't want to run Spyware Doctor. Anyone know what that error means, and how I can get Spyware Doctor to work, and have it NOT crash my PC?