Do you have a Windows 7 Installation Disk? If you do not this is going to be a difficult fix.
What you need to do:
1) Boot using a Windows 7 Installation Disk (If you need help with that, let me know)
2) Right after the BIOS Splash screen, start hitting "F8" repeatedly... like a lot.
3) You will be prompted to a menu, choose "Repair your Computer"
4) If it asks for which installation choose, Windows 7
5) After the automatic System Repair is finished, it will ask you what to do next.
6) Choose "View Advanced Diagnostic Tools" (Or something like that, I am doing this from memory lol)
7) In the next menu, choose Command Prompt.
8) Once there you need to type this exactly, without quotations, also each "_" represents a space.
This scan may take quite awhile. What it does is scan all of your essential windows files and components, and will automatically repair them. You will get a message at the end telling you if it made a repair, or if it did not find anything.
9) Next you are going to run CHKDSK. To do this type: "chkdsk C: /f /r" This will run Checkdisk and it will also scan, and repair any Windows files.
10) Restart your computer after everything is done. Generally this is an hour to 2 hour process.
I hope this helps.