Only showing upper left corner

With roughly half od my games (including new ones), the game will resize,
then only display the upper left corner of the screen.

I've tried fumbling with drivers and restore points and patches and FSAA and
everything else I could imagine. Since it happens on around 10 of my games
that ran before on my setup pre-Vista (and I changed no hardware since)... I
can only conclude that this is a Vista error?

Thank you for your time.