I've tried everything. Sometimes it posts with 1 stick of 4GB DDR2 most of the times it doesn't, and it never posts with ANY 2 sticks of DDR2 wether it's 800 or 667MHz. I really need my pc to do my work so please someone help me out. I have 2 sticks of mushkin enhanced Silverline DDR2 800MHz. 4GB per stick.