I have a 24inch aluminum iMac running the latest versions of Snow leopard. It's a little over 2 years old. I can turn my computer on and all is fine, I can keep it running for hours on end and nothing is a problem. However, the moment I turn it off or perform a restart I get the flashing folder icon??? It takes about 2 hours before I can boot the computer up again. I've tried the following: Resetting PRAM and VRAM Resetting the start up disk information through system preferences pulling an individual RAM module, booting up then trying the same with other RAM module (to check to see whether I have some dodgy RAM) At first I though it must be the hard drive, but why can I run my computer with no problems at all.....I had it running for 2 days, and not a problem!! But, the minute I turn it off...that's it, you can forget booting it up for at least another hour Any ideas would be greatly appreciated!!