Do you have anything on the HDD that needs to be saved or backed up first?
Personally I would boot from a utility disk such a Hirens Boot Disk or the Ultimate Boot CD and check the drives SMART to make sure it is ok. If it is ok then next I would boot from a win7 disk and try repairing the OS.
AS a last resort you can use the OneKey, to the right of your Power button, to begin the Factory Restore process. This will erase the current C: and install windows as if it was the first time it was ever turned on (so there will be LOTS of updates). Be sure to have backed up anything you need FIRST!