TriggerFinger

RAM showed no errors with Memtest86+, correct? Have you tried HDD diagnostics? Use CD image (.iso) of Hitachi DFT or Seatools and run quick or advanced tests (see HDD Diags link on my sig). Remember you need to burn the CD Image file into a blank CD using ImgBurn or Nero. I suggest you check HDD for errors and post back what you find out.