I've got an iMac that's about 3.5 years old (late 2009 version; 21.5 inches; 3.06 GHz Intel Core 2 Duo) and has recently been giving me problems. The 'theme' seems to be "installing something new" / "installing phase of downloading": About 2 years ago I upgraded to Snow Leopard and the installation wouldn't verify. I talked with tech support and they walked me through a half dozen possibilities, but ultimately I had to take the machine to the store, because it downloaded the install, began the install, but failed to complete. More recently I tried to download Mountain Lion. Downloaded the program with no issue. At the installation phase, it'd get to ~95% then would quit because of a verification failure. Apple Support couldn't figure it out (walked me through permissions, etc). After I recently ran an "update software", 5 items downloaded, but couldn't install (error occurred). iTunes informed me of a software update for my iPhone 5. Crashed during the installation and I had to find another computer to restore it (everything was deleted). PITA! I guessed it was either a RAM issue or a permissions issue. I've tried all of what I consider the obvious fixes on permissions... everything in the directory looks okay to a rookie eye. I guess I'm okay taking it to the genius bar, but our Apple Care warranty is out -- any ideas how much I'd be out of pocket? Anyone have a solution or an easy test I can do to figure this one out? I'm assuming someone will need more information, but I'm new to this process so just let me know! Thanks!