i have a HP Pavillion zv5000 AMD Athlon 3000+ 1.8 processor. running windows7, i just bought some ram to upgrade from 512 to 2 gigs win,7 wont boot past the "starting windows" screen but if i take out 1gig and add a 256 it boots fine with a gig and 256, so i formatted back to the original OS that came with the laptop and it works fine with 2 gigs (xp home) this laptop is capable of 2gigs running but wont on Win,7.. the ram is fine and both are matching