Check the temperature on the graphics card with the ForceWare application by right-clicking the NVIDIA icon in your system tray, then go to NVIDIA Display and click on the display you're using. On the left-hand menu, there should be a topic called "Temperature Settings". Report back here when you know how hot it is. You can also put a finger on the graphics card cooler to check if it's really hot even in Windows.
You can also try SpeedFan
to check how hot your processor is, among other things.