I have had that with Windows 7 a few times and there was nothing wrong with my machine and it didn't fix anything either, so who knows what it thinks it's doing.
This may be way off the track here but I got something similar on a Windows XP machine the other day and what had happened was that my account had been deleted (for some reason).
Go into Safe Mode (press F8 on startup) and if Windows opens in Safe Mode then it's not as bad as it seems. Open Control Panel and then open Add or Remove User Accounts from the User Accounts and Family Safety menu and check that your account is still there. If it isn't, add it with the same name you used before and restart and all should be well. If your account is still there, restart and press F8 to get to the start options and see if you can fix the problem from there.