Hey Technology, I have a perplexing problem. I went to upgrade an older machine, Compaq D530, from 768meg RAM to 2gig RAM. The Mobo has 4 slots and will acccept 512meg in each. When I turned it on, it would post but would not boot Windows XP SP3. I started pulling the modules one at a time, thinking I had a bad one. it will boot on 3 modules, doesn't matter which three or which slots they're in, not counting slot one of course. What could be the problem? I don't normaly seek help, but this has really got me stumped. Thanks in advance for any advice.