Can you boot into Safe Mode?
If you can boot into Safe Mode and use the command prompt to run chkdsk c: /r.
If this doesn't help try running sfc /scannow from the command prompt.
When you've booted into Safe Mode type cmd in the Search programs and files[/b] box.
cmd will appear under Programs above the search box, right click on it and choose Run as administrator.
This will open the Elevated Command Prompt, type is the command and then press Enter.
If you can't boot int Safe Mode you can do a Repair Installation.
Instructions for a Windows 7 Repair installation.
A Windows 7 Repair Installation will require a installation disc.
If you do not have a Windows 7 installation disc you can download a free legal ISO image of Windows 7 SP1 at Windows 7 Forums
. You will need to download the same version of Windows 7 that you have installed, This image is hosted by the Digital River store which is an official distribution partner of Microsoft. This is a genuine untouched image which is safe to download.
Attention: If you do have a Windows installation disc, skip Part A and go to Part B, Step 1b.
Part A, Steps 1a - 6a
The ISO image will need to be burned to a DVD in order to create a bootable installation disc.
How to burn ISO image using Windows Burn Disk Image.
Notice: This applies only to Windows 7 and Windows 8, earlier versions do not have this.
1a Place a blank CD or DVD in the tray of your optical drive and close the tray.
2a After you have downloaded the ISO image you want to burn right click on the Start orb, then choose Windows Explorer.
3a When Explorer opens click on Downloads in the left pane. Scroll down till you find the ISO file you want and double click on it. Click on Burn Disk Image.
4a In the image below you will see Dick] burner:, this should be set to the optical drive you want to use. Click on Verify disc after burning if you want to Windows to verity the disc image after burn. Click on burn.
5a In the image below you can see that the green progress bar, when the image is finished burning the bar will be filled.
6a After the image has completed being burned click on Close.
Please note: In order to boot from this DVD you may need to change the boot order in the BIOS so that the CD/DVD-ROM is the first device in the boot order, and the hdd is the second device.
Part B, Steps 1b - 10b
1b) Place the installation disc in the tray of the CD/DVD drive, close the tray and restart the computer.
2b) You will be prompted to press any key to start the installation, I find the space bar handy.
At this point the setup process will load files, this will take several minutes.
3b) You will now need to choose the Language, Time, currency format, and Keyboard or input method that you'd like to use.
After this is done click on Next.
4b) Click on the Repair your computer link at the bottom-left of the Install Windows window.
This link will begin the Windows 7 System Recovery Options.
5b) System Recovery Options will now search your hard drive(s) for any Windows 7 installations. This will take several minutes.
No participation is required on your part at this time, wait till it has finished and the next window opens.
6b) Choose the Windows 7 installation that you'd like to perform the Startup Repair on, then click on Next
7b) Click on the Startup Repair link from list of recovery tools in System Recovery Options.
For a future reference, there are several other diagnostic and recovery tools available in the Windows 7 System Recovery Options including System Restore, System Image Recovery, Windows Memory Diagnostic, and Command Prompt.
8b) The Startup Repair tool will now search for problems in the system files.
If Startup Repair finds a problem with any system files the tool may suggest a solution which you will need to confirm, or may solve the problem automatically.
9b) Startup Repair will now attempt to repair whatever problems it found with system files.
Note: If Startup Repair did not find any problems with system files you won't see this step.
Important: Your computer may or may not restart several times during this repair process. This is normal, you should allow it to continue until you see the Restart your computer to complete the repairs window.
10b) Click on Finish, this will restart your computer.
It is possible that the Startup Repair will not be able to fix the problem. If the Startup Repair tool determines this, it may automatically run the the repair after your computer restarts. If it does not automatically run the repair but you are still having problems with Windows 7 repeat these steps to run Startup Repair again manually.
If the Repair Installation can't repair the operating system go back to step 7b and choose Command Prompt in the System Recovery Options and run the chkskd from there. The commad there would be chkdsk c: /x /r.
After that you should run sfc /scannow.