I have an old dual 1 Ghz PowerMac (Quick Silver) and for some time now I have been experiencing OS crashes. Lately it has been crashing 2-4 times a day. What happens is I'll be using the computer, or it will just be left on with no one using it, and a black window will pop up in the middle of the screen saying to force shut down the computer by holding the power button. I figured this might be caused by some messed up files or something in the OS, so I wiped the hard drive and did a clean install of OS X. It still crashes. Could it possibly be the hard drive which is failing? Sometimes the computer also lets out a weird "beep" sound which is quite loud and then just shuts off. I thought that might be related to a high operating temperature, but I am not sure. The computer is not right up against a wall or in a room that's really hot. I'm wondering if I should purchase a new hard drive and then just reinstall OS X yet again, or if I should just purchase an all new mac pro at this point. If I purhchase a new hard drive for it and find it doesn't help, can I transfer the hard drive to the new Mac Pro, or my other G5 PowerMac?