I first installed windows 7 home premium a few weeks ago, and up until a few days ago it worked fine. Now whenever I try to shut down or reboot the system, it seems to freeze on the "logging off" screen, although the blue circular doughnut still goes round, giving the impression that it's still running. It also seems to refuse to let some programs work although they used to work fine up until this point - iTunes and Safari seem to be at the brunt of the problem. Whenever I click on either of these they very rarely seem to work, with the loading icon on the cursor coming up, then disappearing. I tried a system restore but this resulted in a "catastrophic error" with every date I tried to restore it back to. I reinstalled Windows yesterday and for a short period of time it worked but it has now seemed to slip back into it's old ways. Any suggestions at all would be greatly appreciated!!