I'm not sure if this thread is still ongoing or whether TS found his solution already.
But if you're not as tech savvy enough to use all those frame-per-frame programs (like me ) and you just want to quickly take a snapshot, this is the quick way on WMP.
Open your show, pause it whenever you want to take a screenshot.
Open the WMP menu, go to tools, then to options, then to performance.
Lower your video acceleration all the way to the bottom and apply it.
Print screen and paste on paint.
Ta daaa
Do remember to move your video accel all the way back up once you're done so as to not affect your video watching qualities.
Hope this helps! =)