I'm having a problem with my PC and this isn't the first time it's happened. For a few days now, when I turned my PC on, it didn't immediately start to boot up. The monitor said "No signal" and the machine just sat there although the power light was on and the fans were running. Then, after a few minutes, it would begin to boot as if nothing was wrong. Today I started my machine and it ran ok for about 10 minutes. Then the whole thing froze up and I had to shut it down and restart by holding the power button. When it rebooted, the same thing happened again and again and now finally it wont boot up at all. This happened before about 8 months ago. I ended up taking it to the shop after getting a blue screen. They replaced the HDD and upgraded it to windows 7 and it has worked fine since then. However, they charged an arm and a leg for the work and I dont want to have to go back there again. As this is a recurring fault I figure its a mechanical problem of some sort but I'm not sure what. Any ideas? Thanks for your help.