The official way to find out if you have 4.5 installed (and not 4.0) is in the registry keys :
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full
Relesae DWORD needs to be bigger than 378675 Here is the Microsoft doc for it
all the other answers of checking the minor version after 4.0.30319.xxxxx seem correct though (msbuild.exe -version , or properties of clr.dll), i just needed something documented (not a blog)