I have an older Dell Latitude CPx that still runs Win XP that I use for wireless access in my house. I don't run a lot of apps on this box, just use it for web & music outside my home office. The "B" DIMM slot will not recognize memory. I've installed known good memory into the slot but nothing is recognized. Initially by reinstalling the DIMM, it would work, but even that stopped. Is there a fix or do I have a door stop?