I've been setting up a new machine to do a code review of 1.3 million lines of code. I had installed every version of Visual Studio available to woman and hit a point where I had to know what version of .NET that I had.
I have the memory of a goldfish (ooh, a castle) so I Bing'd the command I needed to run in my Visual Studio command console and found that people wanted me to run regedit and check a key somewhere in some place over some rainbow.
No! Stop now!
Just run the Visual Studio command prompt and type: clrver
That gives you all versions of the CLR running on your machine.
If you have to go to regedit, assume something is wrong. It is an anti-pattern.