Thanks for testing, the result is correct, my assumption was wrong :). Windows 10 replies to this call with MajorVersion = 10 and MinorVersion = 0, which sums up to 0x0A00. Win7 replies with MajorVersion = 6 and MinorVersion = 1, which sums up to 0x0601.   Edit: Please re-test with updated function attached, should show the difference under the scenarios you've tested above. Edit-2: Good info on the technical preview and RTM, added to documentation of function :)...   ConsoleWrite((0x0A00 > 0