.NET框架(不可安装的应用程序?)

So the windows have different versions of .net framework, 1.0, 1.1, 2.0, 3.0, 3.5 along with Service packs for particular frameworks. Now my windows have several versions of the said frameworks and what confuses me is that are these uninstallable or installable? Can I remove older versions If I am just using let's say 3.5 or 4.0 with ASP.NET and Visual Studio?So the windows have different versions of .net