new memory not working in pc - crashes at password prompt

[atarifreakz]

hello

i have an ASROCK K7VM2 motherboard in my totally standard pc - it uses all the on board utilities and has no extra cards - the chip is an AMD ATHLON XP 2000+ - i had 512 mb in it (2x256) i recently bought 2x512mb (1 gb) same spec memory (pc2100 - 266mhz - non ECC) when i put it in and run the pc it crashes at the pass word prompt (win XP) and then restarts - i did manage to get it to stay at this page and the screen had tiny white streeks in it and froze - it runs ok in safe mode - runs ok with the old memory - in the bios i can see the new memory installed ok - can anyone help me as to why this is happening? what can i do? could this memory be bad?

any help appreciated please!