unable to launch both demos

[Wyrd]

It sounds like you have mixed versions of driver files installed on your system. That can happen if you install a new video driver on top of the old one. You can fix by doing a clean driver install.

1. Uninstall the Nvidia display driver ONLY. Don't uninstall any other Nvidia drivers, such as network, chipset, or audio drivers.
2. Reboot.
3. Get Guru3D Driver Sweeper* and use it to clean out your Nvidia display driver files.
4. Reboot into Safe Mode (tap F8 during bootup until you get a boot menu, then select Safe Mode).
5. Run Driver Sweeper again and clean your Nvidia display driver files.
6. Reboot.
7. Reinstall the latest display drivers.
8. Reboot.

* http://www.guru3d.com/index.php?page=driversweeper