I don't know what the situation is but it couldn't hurt to completely unistalled all the old Nvidia files by going to Control Panel and click on Programs and Features in Vista. In XP go to Control Panel click on ad / remove programs. There should be three Programs NVIDIA Display Control Panel / NVIDIA Drivers / NVIDIA PhysX make sure they all are removed. Go to you C drive: to there go to START click on Local Disk (C and you will see the NVIDIA Folder. Just right click and delete. Next find you 258 driver update and click to install when finished re-boot and you are done. Maybe you know all this already but a clean install can't hurt some old files in the NVIDIA folder could be corrupt or have some compatability problems with the new driver files.