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#11
Have you tried to run teh startup repair? Sometimes you have to run it three times before it finalizes repairing your 7 install
For you to backup, in case you can't boot on this computer, the best would be to find another computer where you could plug the HD to and then copy what you need.
BTW, if it started doing that all of a sudden you might have a disk problem, I would advise you to check your HD if can meke this work again.