Reason 3.0 5 Update What Is The Microsoft FrameWork .NET For?

What is the Microsoft FrameWork .NET for? - reason 3.0 5 update

I think I'm having problems with frame of MS. Net ... Since the last update of Windows XP that turns my computer once or twice for no reason in the morning. By using the "Add or Remove Programs" in my system, I see that I've installed versions 2.0, 3.0 and 3.5 ... Do I really need it? ... I'm not really sure what the problem was but my antivirus firewall blocked the connection of the attempt to connect after a few days previously installed.

Any help is welcome!