If you have a non integrated video card (No idea what the term for that is), try accessing the setup for it (Nvidia offers the "Nvidia control panel") and checking the fan settings - it may be set to max.
If this does not work, try entering your BIOS and checking the settings.
It MAY be happening because Windows 7 requires more out of your PC than XP (Which I assume you upgraded from, based on your OS information), so it's attempting to cool it down. Try running HWMonitor (
CPUID) and checking the temps of your CPU / GPU / HDD.