.NET framework initialization error.

okay so i got this error after i installed net framework 4.0.
it says that 'unable to find a version of the runtime to run this application.
can someone teach me how to solve this error?
thks

install net framework 3.5 as said in the guide (although i have 5.0 and it works fine)

er thks i got it done but another error came out.
i get to the login thing,and when i key in my id and password, a microsoft.net framework error came out.
it says unhandled exception has occured in your application.
mind telling me any solution for this?
thank you so much