Got corrupt RAM?

So I recently purchased 4 gigs of dual channel OCZ reaper 1066 DDR2 RAM for my new gaming rig I just bought...and I think its corrupt. When I go to install most games I own(BF 2142, Counter strike/HL2 death match/Day of defeat,Guild wars,Tabula rasa, WoW, the list goes on) or even windows updates(Im running XP SP2) most of the way through the installations my computer claims that there is a file missing from the installation, or in Counter strikes case that there is a corrupt file.I ran memtest it seems like hundreds of times and right off the bat it tells me that m ram doesnt store values correctly. Im considering RMAing the RAM back to newegg but am wondering if it might be a mobo issue and if I should send that back too?

Im trying to get my computer to run correctly, it can perform any task so far except install games and other large programs.

ASUS P5Q mobo
Western Digital caviar blue 80 gig 7200 sata HDD
Diamond 4850 HD video card
Lite-On 20X dvd drive
4 gigs of OCZ reaper pc8500 1066 RAM

Help anybody!?

I found out that one of my sticks is bad, Ive got both of them in and XP says ive only got half of whats installed. And I manually set the RAM voltages in the bios to 2.0(having read multiple forums about my ram needing to have it manually set for performance reasons)But my P5Q pro is brand new, would it still need a bios update? Isnt that a bit tricky?

^+1 for memtest