Weird about WDDM mode for K40m in Windows

Normally K40m should not support WDDM mode in windows, but I was succeeded in doing that - Windows 7, driver 368.39.
But only once, that means I cannot duplicate this success on the same machine for reinstall windows 7, neither on the same hardware for another machine. I don’t know why.
Any hints for this thread will be appreciated!

A successful WDDM mode in Windows 7 is shown below

http://i2.buimg.com/4851/d4eeaf418883f7b2.png