A few weeks ago my computer got where it would not always respond to the mouse correctly which would require a system reboot. While I was trying to work on that I started getting BSODs. The error was not always the same but the most common error was IRQL NOT EQUAL TO OR LESS THAN.
After a week of that I turned off my Vista 64 HDD and and turned on XP-32. Booted up and still had the same problem.
Now the good news..
I stepped up the voltage to the memory and cured the problem with the mouse, leaving the BSOD error. I then stepped up the voltage to the CPU and cured the BSOD.
I did no hardware changes to the system so am not sure exactly why I had the problem. Could it possibly have been a driver upgrade that required the CPU (or another piece of hardware) to use more voltage and changed the voltage distribution balalce?