Windows failed to boot after memory upgrade

[mintmassive]

I'm new to this game and wondered if anyone had any ideas. I just upgraded an Epox EP-4B2A from 256 to 512 DIMM PC133. The computer booted up fine and recognised the memory but then nothing happened. Windows 2000 NT is installed but did not load at all. If the memory is removed the computer works fine. If the current memory is replaced with the old then there are several bios beeps. What's going on?