Just a heads up on the T5500 (or similar Dells) a lot of us bought a few years ago. Though they are built like a tank, I had one go down about 10 days ago. It would boot to the bios but blue screened trying to start Win 7. Error messages pointed to a hardware failure, probably a HDD. First I swapped in a new system battery with no joy. I then swapped in another HHD that had Win 7 installed to see if I could get it to at least try to boot to Windows, no luck. Installed Linux over Windows, would then boot to a black screen but no farther. My last thought (should have been my first) was to pull the CPU riser...boom, booted to Linux. Checked all cpu and memory fans were running, they were all good. I swapped out the memory in that riser thinking that might be the issue, still no boot. Pulled the riser and once again it booted. I pulled a riser out of a second T5500 and installed that in the problem machine...the problem machine booted fine. Installed the suspected bad riser in the 2nd T5500, no boot on the 2nd T5500. So, bad riser. Giving it a close inspection showed nothing obvious. I did note that there appeared to have been leakage from all the caps on the board that wound it's way around a lot of the traces on the back side of the board. A few areas appeared to have corroded the traces. In any case, I purchased a Dell Certified board off of ebay for $44.99 installed the fans, cpu and memory and everything is back to working again.

Moral of the story: If you have one of these machines go down and you're running dual cpus, pull the riser first not last.