Windows2000 SP2, Abit KT7A & 1 GB RAM

Hello,
I need to install to my Windows2000SP2 1 GB RAM. The Abit KT7A supports 1,5 GB RAM, but after installing the boot process is stopped with a BSOD that system couldn`t find file or registry hive system32\config\software… With 1×256 and 1x512RAM modules it works fine, but with 2×512 RAM modules it doesn`t boot. Any idea?