This is a total newbie question - I've never built any computers before but I got my hands on some memory chips and tried to fit them, one didn't want to slot in, the other seem to fit but the computer wouldn't boot up properly (had a blank screen).
My motherboard is ASUS M3A76 but I'm not sure how to id the memory chips , lots of serial numbers which include -
512MB DDR 266 CL2 ECC
512MB DDR2 400 REG-D CL3
If these are the wrong sort of chips what type do I need to get?