If you power up your Windows 7 computer and see an "Operating System Not Found" message in place of your regular login screen, your first instinct may be to panic. This message typically means that your operating system, specifically your master boot record (MBR) has become corrupt. That corrupt master boot record means that your Windows 7 desktop or laptop will not work normally again until the issue is fixed.

Fortunately, it is relatively easy to repair a corrupt master boot record in Windows 7. Fixing a corrupt MBR in Windows 7 is much easier than doing the same thing in earlier versions of this popular Microsoft operating system. All you need is your Windows 7 installation CD and some time.

To fix a corrupt master boot record in Windows 7, just follow these simple steps.
1. Open the drawer to your CD or DVD drive and insert your Windows 7 installation CD. Close the drawer and restart your computer.
2. Wait for the computer to boot from the CD. If you see the "Operating System Not Found" message you will need to restart your computer again. This time watch the screen for a "Press XX for Setup" or similar message. Press the appropriate key, go to the Startup menu and change the boot order to put the CD first.
3. Select the default language, time and keyboard input options when the Windows 7 CD starts up. Click Next to continue.
4. Choose the Repair Your Computer option and select the System Recovery window. Select the Command Prompt option.
5. Type cd boot to change to the c:\boot folder. The MBR repair utility is located in the boot folder on the drive where Windows 7 is located.
6. Type Bootsect /nt60 C:\ at the command prompt. This command starts the command that fixes the boot sector on a Windows 7 computer.
7. Wait for the utility to finish running, then restart your computer. The PC should come up to the normal Windows 7 login screen. If not, your PC has other issues and will need further troubleshooting to resolve the issue.