On the Start menu, choose Run.
In the Open box, enter regedit.exe.
You must have administrative credentials to run regedit.exe.
In the Registry Editor, open the following subkey:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP
The installed versions are listed under the NDP subkey. The version number is stored in the Version entry. Starting with the .NET Framework 4 the Version entry is under the Client or Full subkey (under NDP), or under both subkeys.
You can test whether the .NET Framework 4.5 or the .NET Framework 4 is installed by checking the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full subkey in the registry for a DWORD value named Release. The existence of this DWORD indicates that the .NET Framework 4.5 has been installed on that computer. The value of Release is a version number. To determine if the final release version of the .NET Framework 4.5 is installed, check for a value that is equal to or greater than 378389.