Occasionally( on 4th or so start) when I power up my PC it will get to the login screen, I then enter my password and hit enter and the PC hard freezes where I have to turn off the power and then restart it. It has always started and logged on OK on the second attempt. I don't know what else to add other then it has never done this before I installed windows 7. After further starts I've noticed that it doesn't freeze if I enter my password right after the login screen appears, if I wait even a couple minutes that seems to be when it freezes.