Did you for some reason do a disk compression?
I would try a startup repair using your Windows 7 install disk or system repair disk. If you didn't get one with your laptop, you can download a trial image of the same version from
DIGITAL RIVER.
If a startup repair doesn't fix it, you can try a repair install that will not delete your data or programs.
THIS is a step by step tutorial to do the repair install. If you do that it will require you to do your Windows 7 updates since SP1, and you will need to activate with your existing Windows 7 key.