Just making a quick reference for myself of the info found on msdn.

Take a look at the following registry keys

Frameworks 1 – 4
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP

Frameworks >= 4.5
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full\Release
where
378389 = .NET Framework 4.5
378675 = .NET Framework 4.5.1 installed with Windows 8.1
378758 = .NET Framework 4.5.1 installed on Windows 8, Windows 7 SP1, or Windows Vista SP2
379893 = .NET Framework 4.5.2