its a bug in windows this type of thing can also be done in MSPAINT so you cna all try this...
open your web browser and find an online video to watch juss go video google for now, put your browser in full screen and play the video, have MS PAINT running, now take a print screen of the video window and paste it into MS Paint, now go back to the video and then back to MS paint and you can view the video while in MS Paint....weird ah??!!?
EDIT dont think it works on video google try a windows media video but thru your web browser