My iMac has been behaving noticeably erratic over the last few days. The Windows partition is all but useable and my OSX partition is beginning to display similar signs. Finally got the thing booted in Windows safe mode and ran HD Tune. The test crashed after it was discovering the 6th bad sector! Just like the title said, this will be the fourth hard drive going bad in a little less than four years. I don't need an explanation as to why, because there are many, but the only thing I can correlate it with would be heat. Yes, drives have a 100% fail rate, but this is absurd. Time for me to open her up, replace this failing HDD and then quickly sell it to buy a 2013 model. No better time to get a new one than now I suppose. I just can't believe my luck.. At lest I have multiple backups.