It could be that usual issue of updates in the background that can take a few days. One of our office machines took a dive after a Tuesday update so we looked hard at it and it was .NET recompiling in the background. Not so much background as it claimed it should be. We did more digging and found a few fixes but settled on waiting it out.
Also, if this was a certain type of upgrade you would reinstall the drivers for your PC. This is far from automatic.
I upgraded my PC from Windows 7 Home Premium to professional so as to make use of the 24GB installed. Bad news is the PC is now stupid slow. Takes about 5 seconds to do anything.
Any suggestions what might be wrong or need adjusting?