I have an Acer 5920 laptop that recently had a bug in the boot sector. I wound up reinstalling Vista on another partition to be able to get back to the original installation that came with it. Now that it is back working I noticed that only 2G of the installed 4G is showing up in the system or the BIOS. I opened and looked, removed and replaced the two memory sticks and still only 2G will read in the bottom slot. Both sticks read in the bottom slot and the system won't boot up with one in the top slot. Is this a sign of a dead motherboard, or try something else.