I have an OptiPlex 390 64bit Pentium Dual Core desktop.  It came with 4gb of memory, and I recently contacted Dell to see if I could add more memory.  They informed me I could add 4gb more, and I purchased the VisionTek 4gb CL9 1333MHz DIMM module.  I installed it, and even though it shows 8 gb installed, there is 4.8gb hardware reserved.  I have updated the BIOS, unchecked the maximum memory setting, and updated the BIOS to factory settings.  All to no avail.  Any help would be GREATLY appreciated!