You can try to reinstall windows. If your HDD is dead or on the way out you are going to get tons of errors.
I would put reinstalling windows 7 as your last resort, but the list for trouble shooting this is honestly short and has already been said above.
But.... give the reinstall a shot... if it does not work let us know. We can point you in the direction to replace your HDD. Its a very easy component to replace.