Any advice on fixing a full screen problem possibly vista related?

[Gabby]

My computer will not go in to full screen, on games, youtube, even windows media player.. On games it just won't go. On others like youtube i can hear the audio but my screen is just black until i hit escape.. I have windows vista and am new to it so i'm not sure if it could be vista related. If you have any advice on how to fix the problem it would be much appreciated.
Something i forgot to mention was i haven't this problem until recently.. Before this i had no problems viewing in full screen mode.

[Brent B]

sounds like youre missing codecs or something. or display driver?