what FSB is your system running at? what cpu... if you're running a Q6600 or something... no dw it doesnt matter what cpu as long as you put it at 1:1 ratio with the FSB. then, drop the timings down one at a time until it fails to post or errors in memtest. then bring it back up just enough so that it's stable.
^same as me bro i got 2 gig kingston 667 LOL... depending on your BIOS (mine doesnt have a divider...) put the divider at 1:1 or like me, drop the RAM speed to 400 if you can (only option apart from 667 was 533 for me ) and drop the timings to 4-4-4-12.