first thing, reinstall the nvidia drivers by checking the clean install box under the box that describes the components that will be installed (install every thing). if that doesn't speed up this system then...
remove all graphics drivers from add/remove programs. ( nvidia / amd )
(not really needed because win7 doesn't really mess up when you change graphics cards, but you want all the driver parts to be the same version, so removing all gpu drivers is the easy way yo do it)
then run driver sweeper from safe mode.
then install the latest graphics driver for your system, using the clean install option.