If Windows isn’t booting properly and won’t even allow you to use the startup repair option at boot, you can run startup repair from a system repair disc or recovery drive.

Launch Startup Repair From a System Repair Disc or Recovery Drive You may be told you need to use a Windows installation disc to repair your computer instead. In some cases, the startup repair option in Windows 7 may not be available. Select “Repair Your Computer” and run startup repair. You’ll see the Advanced Boot Options screen, which is where you would launch Safe Mode from. Next, turn it on and keep pressing the F8 key as it boots. First, power the computer completely down. If Windows 7 won’t boot properly and doesn’t show you the Error Recovery screen, you can get into it manually. Windows will attempt to find and fix problems that can prevent your PC from booting. After it does, select the “Launch Startup Repair (recommended)” option. Windows will prompt you for your keyboard layout and a username and password for your PC.