This is from Nvidia directly. It covers all the issues and suggestions (above) plus several others, as follows:
"My system keeps crashing/locking up. How can I fix this?
There are dozens of reasons that can cause a system to lock up, especially under intense graphical situations. First of all, verify that your system supports the minimum requirements provided by your graphics card manufacturer. Primarily, make sure if your graphics card is an AGP card, that your motherboard meets the AGP 2.0 specification. If your motherboard does not meet the AGP 2.0 specification, then it may become unstable, especially when you are running 3D applications. If you are unsure if your motherboard is AGP 2.0 compliant, please contact your motherboard manufacturer and ask them if your particular motherboard is AGP 2.0 compliant. Also, your system should be running at least a 235-watt power supply (250-watt is preferred.)
If your motherboard does meet the AGP 2.0 specification, then check that your motherboard is using the latest BIOS. You can locate the latest BIOS from your motherboard company’s Web site or from the Web site of the company that assembled your PC. Please contact the maker of your motherboard for assistance in flashing your motherboard with the latest BIOS. Flashing a motherboard BIOS is very difficult, and if performed incorrectly, can permanently damage your graphics card. NVIDIA assumes no responsibility for any problems incurred as a result of flashing your BIOS.
You may also need to update the AGP controller drivers for your motherboard. Some smaller computer retail stores that build custom PCs often tend to forget to install the drivers for the motherboard. This will lead to lockups when running in 3D mode. Please check with your motherboard manufacturer for the make and model of your PC chipset, and download the latest chipset drivers from their Web site. The drivers are available from:
VIA chipset -
AMD chipset -
ALI chipset -
SIS chipset -
Intel chipset -
If you are upgrading a graphics card, then make sure the drivers from your previous graphics card are properly uninstalled. Please contact the manufacturer of your previous graphics card to find out how to properly uninstall the drivers. If the drivers are not properly uninstalled, they can conflict with other installed drivers, and slow down the performance of your graphics card.
Be sure that there are no programs running in the background that can affect the stability of your system. Virus protection programs, peer-to-peer software, and crash guard utilities can affect the stability of your system when playing 3D-intensive applications. Disable these utilities and any other programs before you run any 3D applications or games.
With more devices being included in today's PC systems, it forces system builders to install components that share IRQ's with other devices. Some components do not like sharing IRQ's and can lead to system lock ups.. To check this, click on the Start button -> select Programs -> select -> Accessories -> select System Tools and then choose System Information. Click the plus "+" sign next to Hardware Resources to expand the list and then click on IRQs. Look for your graphics card on the list. Generally, the graphics card should have its own IRQ and not be sharing one with any other device. The only thing that should be sharing the same IRQ as the graphics card is an “IRQ holder for PCI steering.” If you have anything else sharing the same IRQ as the graphics card, you must change that device's IRQ assignment. The easiest way to do this is to simply to move the device, which is sharing the IRQ with the graphics card, to a different PCI slot. Some motherboards also allow you to force an IRQ. Check with your motherboard manufacturer to see if this feature is available on your motherboard."
There is plenty (above) to digest and tryout. However, your problem may ultimately be with your motherboard and it's bios so I'd get intouch with whoever built your rig and see if they can help!
good luck
