A few days ago my wife was on our 24 inch iMac and told me she was frequently getting the spinning beach ball. Then all of a sudden one morning it wouldnt boot into OS X (Snow Leopard), the spinning wheel just kept going in the Mac boot screen. Yesterday I reformatted the hard drive and reinstalled Snow Leopard. Again the spinning beach ball started showing up frequently. We went out for dinner and when we returned I walked over to the iMac and there was a screen with a question mark within a folder blinking. I restarted it and just got a blank gray screen like the boot screen without the apple logo. I restarted it again and it finally booted back into OS X. So my question is what is the most likely problem? Is this a sign of a failing hard drive or something else?