I've had the same pair of 1gb gskill ddr2-800 installed since summer 06. Previously they were running in dual channel and showed up as 2gb in bios, cpuz, system properties, etc. Now suddenly, within the last couple of months anyway, I've apparently lost 512mb of memory. One stick is showing up correctly as 1gb and the other 512mb. I've tried different slots, each stick separately, and every combination possible in the 4 available slots on my m2n-e motherboard. The one stick shows up as 512 regardless of scenario.
i tried switching around the slots some more just to be sure. it seems that the one always registers as 512 when put in any slot by itself. the other always registers 1 gb when by itself.
if i insert both sticks, then either one may show up as 512 in cpuz. it seems totaly random when both are used. i'm not sure how accurate cpuz is at determining which slot is actually registering as 512. maybe it just knows the total is 1536 and assigns 512 to one of the slots at random because i can't see a pattern.
This is so obvious as to be painful. If one stick always shows as 512MB and one stick always shows as 1GB, then IT'S THE STICK OF RAM.
it's not always the same stick of ram when i look at cpuz, but like i said above i don't know how accurate that is. it's always the same stick if i put them in separately though so i guess mem is the culprit, not the mb.