My XPS 8100 has 4 dimm slots two with white tabs and two with black tabs. When I purchased the system all 4 slots were populated with 2GB memory sticks for a total of 8GB and worked fine. The system lay dormant for several years, when I decided to bring it up to my cottage. I now have only 4GB available for windows which makes it run very slowly. After some lengthy investigation I found that the memory sticks in the two black tab slots were not being recognised, with the white slots empty, the computer would beep 4 times and nothing would show up on the screen. However if I moved the same two memory sticks to the two white dimm slots the system would go into the Bios then launch windows. I have tested all 4 of the memory sticks in the white slots and they all worked fine so it's not a bad memory stick. When I have all 4 sticks installed It still works but reports that only 4GB is available. Now this is where things get weird, windows reports 8GB installed but only 3.76GB available.
Also would it be possible to install two 4GB dimms in the two working slots for a total of 8GB?