ok delete that use2.0, if nothing much changes with changing the drivers, more than likely nvidia just used the same drivers for thier "newer" beta version; try this: uninstall all drivers, and attempt to use the microsoft graphics drivers
EDIT: if that doesnt work try other games, if they are all sluggish its probably a driver issue, if not, go into the nvidia panel and disable AA and AF for all games permanantly, usually AA and AF create problems with halo PC and CE...