irql_not_less_or_equal bsod after ram update

ok so i have been working on a buddys computer. he decided to do a ram upgrade a while back so i got him some 184 pin ddr 400 pc3200 cl3-3-3-8. at first we just got 2x 1 gig sticks. we added them to his existing 512 sticks for a total of 3gb. everything ran smooth. he then decided to buy some more ram, with a different timing, so i ended up buying those from him and got him another set of 184 pin ddr 400 pc3200 cl3-3-3-8 (different brand) to match his first purchase. we keep getting irql_not_less_or_equal bsods. it will never happen while i am there but he has taken pictures. keep in mind the error only happens when 4 gigs are installed, weather the timings match or not. all sticks are rated at and are running at 2.6v. in the pc health section i noticed that the 12v+ line was running at 11.96. would this be the problem even though its only 4/100 of a volt? what else could i check? i dont see how it could be the processor since it only does it with 4gb ram.

 

It may not be a problem with any of the ram, but maybe one of the slots is going bad. Also, check the slots for any potential dust. Dust can cause things to short out.

I would run some type of Memory Tester and see if it's spitting out any issues.

http://www.memtest.org/#downiso

 

Download and rin memtest86+
This needs to be written to CD and booted from.

Run this with 1 of the new 1GB sticks of RAM at a time as these are most likely to be at fault.