Help diagnose Read Write Error ram module socket not being recognized Dell Inpiron 5100.

 
Ram socket faulty or Motherboard faulty or BIOS issue.

Help diagnose Read Write Error ram module socket not being recognized Dell Inpiron 5100.

History: Had 2 ram modules at 256mb and then one day started getting read/write errors on bootup. It would only recognize 256mb. I thought it was the ram so purchased two Kingston KTD-INSP8200/512 mb ram modules. It worked for the first couple of boots then started with the Read/Write errors on bootup and not recognizing the 2nd ram. Returned the ram and received new ram to make sure it is not the ram. Once again it worked but only once and on the next boot the Read/Write errors started again and recognizing only half the ram.

Hardware Stats:

Dell 5100

1Gb Ram (2 Kingston KTD-INSP8200/512 mb ram)

Bios: A32 (most uptodate)

WinXP SP2