All the memory is DDR 400 and it should be okay, but it is not recommended to mix different make RAM sticks. Also, 1GB system RAM is not enough RAM for Windows 7, and this "old" motherboard might not support Windows 7 at all. XP Service Pack 3 should work though. Try removing one memory stick, have no USB devices installed except keyboard and mouse. Disconnect all but one hard drive and make sure that the bios sees it, then start the XP install