Use System Restore when Windows fails to start.

If you have enabled System Restore you can use it when you fails to boot into Windows.

How to do:

Restart your computer.

Press F8 before the Windows Logo displays. (Keep pressing F8 from the starting itself, if you hav'nt understood when)

Then the Windows Boot Menu displays.

Select Safemode With Command Prompt and hit Enter.

Windows loads to Command Prompt.

Then type the following:

%systemroot%\system32\restore\rstrui.exe and hit Enter.

That loads the System Restore window. Continue as usual restoration