DRIVER_IRQL_NOT_LESS_OR_EQUAL is usually bad ram. This article should help as it shows you how to diagnose bad RAM. It actually specifically mentions that error in the article as being a RAM issue:
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Try this out, It's titled to be for notebooks. But it also applies to regular PC's as well.

http://www.technibble.com/laptop-data-recovery-how-to-rescue-data-off-a-dead-notebook

Yeah I know I am kind of digging up an old thread but I have a very useful site to answer this question.

http://www.technibble.com

It is a resource for people wanting to become computer...