The most common cause I run into are drivers. One lovely is when an owner accepts a driver from Microsoft. "Lovely." The next common cause I run into is heat related. Many owners are blissfully unaware about dusting out the machine every 6 to 12 months and it's been warm here.
I can't write it's the software in your post causing this.
I have a year old dell 8400 running windows xp home. I recently upgraded my security software from norton security suite 2004 and zonelabs firewall (version 5.5) to zonealarm internet security suite 2006 and webroot spy sweeper version 5.0 (i was running free anti spyware programs before). After running the internet suite and spy sweeper for about 2 weeks I got an error message on a blue screen saying that windows had been shut down, along with "IRQL_NOT_GREATER_THAN_OR_EQUAL" I rebooted as instructed and was able to use the computer for about an hour before I got the same message. Both times that this happened I was using mozilla firefox (I only have ietab installed for extensions), and zonealarm and spysweeper were running in the background. I am very diligent about getting updates, and everything on my computer was up-to-date and running just fine, until I got this error anways. In the end I reinstalled windows and all of my programs, restored my documents, picutres and music from a backup file and was able to run everything just fine for about 2 weeks, only to recieve another blue screen error message. Has anybody encountred this before or know of a solution? I had the zonealarm antispyware turned on the first time, and after the reinstall I turned it off.