Find Framework installed

In this case, you might wonder what .Net framework version you have or do you have the so-called latest .Net 3.5 framework?
OK, general end users can use either one of these ways to check the .Net framework version:

Query the User Agent String of Internet Explorer web browser. This is the easier way, I think, as every Windows bundled with IE! Although you need to remember this simple, one line JavaScript:
javascript:alert(navigator.userAgent)

Other way is to get into Registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP

3 Way is to check through Windows Application:

Environment.Version property of .Net framework. For example, this simple C# source code can be compiled to a .Net console program that shows .Net framework version installed: using System;

class Version
{
public static void Main()
{
Console.WriteLine();
Console.WriteLine(".Net Framework Version {0}",
Environment.Version.ToString());
}
}