I had this same problem a few months ago. It's almost always caused by a driver problem. However, it's difficult to determine which driver is causing the problem because when you get the infamous blue screen you don't get any specific information indicating a driver name. Have you updated any drivers recently? If so, try uninstalling them and restoring the original ones.
If this doesn't work try using the driver verifier tool that comes with Windows. You can find the directions to use it at
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/ddtools/hh/ddtools/dv_7g8j.asp , or do a search on "driver verifier" in the Microsoft webpage. It's only available on Windows 2000 and XP.
Anyway, it's simple to use. Open an MS-DOS prompt window and type "verifier". Then set it up to check every driver for IRQL_NOT_LESS_THAN_OR_EQUAL errors and restart your PC. It will restart extremely slow because it's doing its verifying work on every driver. Proceed to run the application that hangs up your PC. Then, when you get the blue screen, it will tell you the name of the driver that's causing the problem. In my case it was due to an "updated' audio driver I downloaded from the Microsoft webpage. I uninstalled it and restored the original driver that came with my motherboard and the problem was solved.
From this experience I learned that if my drivers are working correcly, I should never download "updated" drivers from Microsoft.
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