How to Perform a Windows 7 Startup Repair

Accessing Startup Repair To begin, you’ll need to access the Advanced Boot Options menu. Follow these steps:
Turn off your computer and wait a few seconds.
Turn it back on and immediately start tapping the F8 key repeatedly until the Advanced Boot Options menu appears.
Select “Repair your computer” from the list of options and press Enter.
If you have a Windows 7 installation or recovery disc, you can also boot from it and select “Repair your computer” from the System Recovery Options menu.

Using Startup Repair Once you’ve accessed the System Recovery Options menu, follow these steps to run Startup Repair:
Select your keyboard layout and click “Next”.
Log in with your administrator account if prompted.
Click “Startup Repair” from the list of recovery tools.
Windows will begin scanning your system for issues and attempt to automatically fix them.
It’s important not to interrupt the Startup Repair process. Allow it to complete, which may take several minutes. Once finished, your computer should restart and boot into Windows normally.

When Startup Repair Fails If Startup Repair is unable to resolve the issue, there are a few additional steps you can try:
Run CHKDSK (Check Disk) to scan your hard drive for errors and attempt to fix them. To do this, select “Command Prompt” from the System Recovery Options menu and enter the following command: chkdsk C: /f /r (replace “C” with the letter of your Windows drive if different).
Run the System File Checker (SFC) to scan for and repair corrupted system files. Open an elevated Command Prompt and enter sfc /scannow.
Use System Restore to roll back your system to a previous restore point when it was functioning properly. Select “System Restore” from the System Recovery Options menu and follow the on-screen instructions.
As a last resort, you may need to perform a clean installation of Windows 7 using your installation disc. This will erase all data on your system drive, so be sure to back up important files first.

See also How to Enter Safe Mode in Windows 8 and 8.1 for Troubleshooting