crashing p.c.

hi all and thanks for letting me be here.
anyway i need a little help as i new to this dont know what to do here goes= i just bulit me p.c. up MSI k7n2 delta ILSR with 2.8 amd with a 120gig maxtor serial ata hard drive and a fx5600 (msi again) anyway heres whats happening i got all the updates and even all the windows updates and drivers (still did the same problem even without the updates) but eveytime i try to play a game i.e. mohaa or call of duty demo me p.c. crashes and most of the time says "driver IRQL is not less or equel than" any help would be gratfull cos its been like this for about weeks now.
o and same with other game as well .
thanks in advance dave

o and i forgot to tell u that the drive is on a serial slot and is the only drive installed none at all on the IDE just dvd drive.

Have you overclocked your CPU at all?

no eveything is as it came out of the boxs and so is bios etc.
no chages at all, 166 fsb witch is right for the cpu as auto is set in bois

dam just when u think u have been out to buy the best what i could affort then u have a thick **** like me putting together

Is your PCI bus locked? I used to get that error on my Asus A7V333 when I overclocked the PCI bus.