Installed new ram, not working correctly

I installed two new 128mb sticks in an old gateway and when I start up it brings up the "Windows did not start up correctly" screen and asks me if I would like to start up in the various modes. No matter which one I try it won't start up and reboots back to that screen. I also tried reinstalling windows, but when it goes through the necessary load ups it reboots back to the same place. My bios settings recognize the two new sticks and I am almost positive they are comptible with my system, so I am not sure what to do.

one of the RAM sticks is faulty (or both)

Or your powersupply is delivering really flakey voltages