When it was just yesterday why didn't you try System Restore to yesterday?
IF you have your windows 7 os disc (which should've came with your pc) you can do something called an "In-place upgrade" This is something that reinstalls all windows stuff and can fix many probs with your pc. I did it on my vista computer and it works 1000000000000000 times better now.
(Check that you have plenty of free disc space and close all programs)
Just insert the disc, and a screen should come up with a button that says " Install Windows", click that and a screen will come up and follow the directions, somewhere along the line there should be a screen which asks what type of windows install you'd like, you should click what i think should be upgrade. then just wait until it finishes and it should fix your probs.
This keeps all settings. But you'll have to reinstall the service pack, and internet explorer. This also clears all temporary items.
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