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.

Update/this is happening everytime that I power up my PC now. The first time it freezes between login and desktop, if I them power off and restart it usually starts fine. this is also kind of a bump so maybe I can get an answer.

You seem to be having the exact same problem I have. When my computer is shut down over night, for atleast six or so hours, when I power it up, it gets to the login screen. I can then login, sometimes, and within a few minutes it crashes with a BSOD. The only way to get it to stop doing that is to hold the power button and manually shut it down. After that, my computer runs perfectly fine. It is only EVER when I boot my computer up for the first time after a long period of being shut off. Check out my thread, maybe it can help. I am still working on my issue.

http://www.techspot.com/vb/topic143286.html