I have more PC problem

When I finished my PC 4 days ago I installed 512MB SDRAM one PC100 module and on PC133 made by Micron with the two modules installed, windows installation would give an error, with only on PC100 module I managed to install windows and to make the PC work but the PC started restarting itsself I didn't pay much atantion because I tought that it was a power loss but now it restarts when I try to copy a CD or when I play more that 20 minutes NFSU 2, or just surfing the internet.
Do you think that the memory is the problem?
I ask because I tried evrything lowering the CPU FSB to 100MHz (200DDR) to comply with the memory rating, but still it restarts.

Sny help would be apreciated.


CTISTI