Very good article showing how to repair a Windows 7 insallation that may have been corrupted. The only downside to this is that you will need to be able to access Windows in the first place to do this repair.
If you are struggling to boot into Windows, try booting in to Safe Mode with Networking, if it boots correctly in Safe Mode, reboot again and wait (a very long time) and see if it boots correctly.

Good luck

http://www.pcworld.com/article/243190/how_to_repair_a_corrupt_windows_7_installation.html