Now I'm getting the IRQL_NOT_LESS_OR_EQUAL error also BSOD...
These are generally RAM-related errors. Try running memtest for a few hours and see what result you get.
EDIT: ...saw you mentioned memtest freezes on you. I'd venture to guess your issue is in fact RAM-related. If you've got more than a single stick of RAM in your system, try removing one and testing again.