A few weeks back I started to notice that when I powered up my unit it took a few minutes to boot up. The fans all started right away, but it would take several minutes before the beep, and then the first screen acticity appeared. Then, this past week, without warning the computer would go dead. Overall it does not lose power since the fans never stop running, but suddenly the screen just goes black. I timed the cycle and it takes about 4 minutes to boot, then it run normal for 5 or 6 minutes, then it goes to black, and after another 4-5 minutes it boots again. Last night I opened the case and discovered that one small fan on the motherboard had stopped turning. With a gentle nudge it started up again. Maybe this caused the motherboard to overheat and shut down the system? Just today after it went dark again it ran for over 10 minutes with no boot. I did try to defrag, run virus scan, check disk for errors...the machine will not run long enough to complete any of these tasks. Could this be a machanical problem with the hard drive or perhaps the power supply? Any advice would be greatly appreaciated. I have all of my data backed up, but I just don't know what to do to troubleshoot this problem..

You'll need to have a closer look at htat fan. If it's the CPU cooling fan, it will cause exactlly the problems you have described. If it's clogged with dust, clean it (use a brush not a vacuum cleaner). Otherwise you might need to replace it. Leave the HDD alone, it works hard everyday and as soon as something goes wrong, you blame it!

If it is the CPU heatsink cooling fan, buy a quality fan with ball bearings instead of sleeve bearings. Same with any other case cooling fans.