Hi,
Try going back to a known good Windows 7 restore point. Alternatively, you could try the below suggestion:
You might need to reinstall all of the different versions for MS Net framework on your PC. Before you attempt to do this, open up the RUN command and enter the following: %systemroot%\Microsoft.NET\Framework
The above will tell you which versions are installed on your PC. Make a written note of each version. Now go into the Control Panel --> Programs and Features and delete each version. You now will need to re-install each version starting with the lowest, apply any Windows updates (run the update process) and then install the next version etc..