I suggest that you uninstall any .NET Framework software installed on your computer and reinstall it by downloading a copy from Microsoft Downloads web site. Please follow the steps provided below to uninstall a program in Windows 7:
1. Click on “Start” and then on “Control Panel”.
2. Click on “Programs” and on “Programs and Features”.
3. Select the .NET Framework programs installed and click on “Uninstall” on the top.
After uninstalling all the installed .NET Framework software, download them from the Microsoft web site link provided below and install them.