How to Fix Unbootable Windows

1. Use the 'Last known good configuration' option. Upon boot up, a black screen may appear asking you to load the last known good configuration. Select this option to load the operating system. If the computer still fails to boot to Windows, the 'backup settings' of the computer may also be corrupted.
2. Use the 'System Restore' feature. When you have this feature enabled in your system, it automatically creates 'restore points' or backup copies of your computer every 24 hours. To use this feature, reboot the computer first. When you hear a single beep, press F8, select 'Safe Mode' and hit 'Enter.'
3. Wait for the computer to boot into 'Safe Mode.' Click 'Start,' 'All Programs,' Accessories,' 'System Tools' and then 'System Restore.' In the window that appears, select 'Restore my computer to an earlier time,' and then follow the instructions to finish the restoration process.
4. Use 'Startup Repair' if you are using Windows Vista. Insert the Windows Vista installation disc into your optical drive and reboot the computer. When you are prompted to boot from CD, hit 'Enter.' If the computer does not prompt you to 'Press any key to boot from CD,' you will need to configure the computer to make your CD/DVD-ROM as your first boot priority (see Resources).
5. Select 'Repair your computer' on the next screen that appears. Select the operating system that you want to repair, and then 'Next.' Select 'Startup Repair' in the System Recovery Options menu and wait for the computer to start making the necessary repairs. The computer shall reboot once repairs are done.