That's because you're looking in the wrong place.
Taken from here:
To find the installed .NET Framework versions manually (versions 4.5 and later):
1. On the Start menu, choose Run.
2. In the Open box, enter regedit.exe.
You must have administrative credentials to run regedit.exe.
3. In the Registry Editor, open the following subkey:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full
Check for a DWORD value named Release. The existence of the Release DWORD indicates that the .NET Framework 4.5 or newer has been installed on that computer.
The registry entry for the .NET Framework 4.5.
The value of the Release DWORD indicates which version of the .NET Framework is installed.
Value of the Release DWORD:
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