My Dell Latitue E6500 laptop all of a sudden started locking up. It didn't seem to be a windows problem because it locked up even in safe mode and even just at a command prompt. I couldn't tell if it was a memory problem or a hard drive failure. I called Dell tech support and they walked me through a built-in diagnostic program. By turning off the machine and then holding down the "fn" key while pressing the power button to turn the machine on it went into a low level diagnostic. It passed all the memory tests but failed on a hard drive seek test. They are sending me a new hard drive but I've decided to replace it with a solid state (SSD) drive - $400 for a 160gb from Amazon.