Ram trouble or motherboard ?

I have been suspecting for quite a while that I have some faulty hardware due to some weird behaviour by the PC, but I've yet to prove it. Does anyone know of a good overall test utility I can try ?

This weird behaviour includes random crashes of applications that usually don't crash, freezing from time to time and often several BSOD's with "DRIVER_IRQL_NOT_LESS_OR_EQUAL" error (or something to that effect).

This seems like a memory problem, but I have another PC with similar symptoms and replacing the RAM never fixed it. So could it be the motherboard ? And how can I be sure ?

 

Post the Exact Blue screen error message

If you suspect memory problems run Mem test, any errors = bad memory

 

Like I said, a BSOD with IRQL_NOT_LESS_OR_EQUAL and usually Stop 0x0000000A (4 sets of hex numbers here).

Pretty much this error