It's not uncommon for me to leave it running. One day, after about 3 hours, I returned to the PC and everything was frozen, nothing would respond, key board, mouse etc. I cold booted the machine. Upon boot up, it freezes, actually it seems to be stuck, I see a Black screen with the Dell and Inspiron Logo, a blue bar that is half filled (blue bar does not fill to 1/2 way. it boots up to that spot), and commands "F2 Setup" and "F12 Boot Options" are displayed. The computer does NOT respond to F2, F8 or F12. It's frozen in time. I plan to trouble shoot and take the HD off this computer and attach it as a slave to another to see if I still have "read" capabilities. I may even take a previous HD with an OS and attach it this machine to help me further diagnose the problem. I've already tried the rescue disks and nothing happens.