My experience with the IRQL_NOT_LESS_THAN_OR_EQUAL BSOD has been wide and varied. Windows knowledge base suggests that this is because of two modules trying to access the same IRQ. This error will appear more when using resources that share the same IRQ, i.e. a sound card and video sharing same IRQ will crash system during games and other programs that use these devices more frequently and intensively; where as, running Word or Excel will not show an error. From what I gather, this problem DOES have to do with IRQ’s –rather IRQ levels. Possible situations that cause this conflict would be:
1.     Installation of Roxio products (EZ-CD creator, Video Pack 5.0, etc.) Possible BIOS (aka device drivers) conflicts include: acpi.sys (Advanced Configuration and Power Interface) and ntfs.sys (NT File Structure).
2.     Setting CMOS settings incorrectly. Look for PnP OS options, and try to free up IRQ’s for windows to use. Disable COM ports if you do not need them. Try setting OS to PnP. Also, try switching physical locations of interface cards. (The AGP slots in most motherboards share an IRQ with the slot next to it.)
3.     Use of programs that tax system resources. In my case, Pulldown.exe (deals with video encoding), Uudecode.exe (used to combine binary newsgroup posts.), and other DVD tools during the creation of VOB’s.
4.     Bad RAM. Although this is a very rare occurrence, in my experience, it is very possible that bad RAM can cause this error. I have never received a DIMM that was faulty (In 15 years), but I don’t buy cheap DIMM’s either. A colleague of mine says that he corrected this problem after replacing a suspected bad DIMM.
5.     Installation of a new device that has not been properly configured or doesn’t have the correct driver installed. Try freeing up some IRQ’s for the OS to use in the CMOS. Disable COM’s and try to reproduce the error.
6.     Corrupted page file due to improper shut down or BSOD. In XP, Right-click on “My computer”, select “Properties”. Then click the “Advanced” tab, click “Settings” in the “Performance” area and another window will appear. Click the “Advanced” tab. In the “Virtual Memory” section click “Change” button. If you have a custom setting write these numbers down, then tick the “No Page File” button. Click ok-ok-ok. Then reboot the system. Repeat the process except correct the window to reflect your original settings reboot again. Sometimes this will temporarily correct the error.
Please continue to test and change system setting (as much as you feel comfortable with) until we can reach a final solution to this problem. Don’t tip-toe around suspect programs because they crash, continue to use them and find solutions so we can put an end to this problem.