You'll just have to reinstall & not update those drivers the next time...
Remember, Windows 8 Developer Preview is pre-beta software, only meant as a basic proof-of-concept framework; while it may look it, it's not a fully-fledged OS & all the new graphical gumpf they've added-in with the Metro UI is only optimised to work on the specific trimmed-down version of Windows 7 they built it on.
Change the graphics drivers, even to "better" ones, and you undermine the whole architecture...
And so, I can only say: Better luck next time!