What would happen if you used a video card that uses more power than your computer power supply?

i have a computer with only 250watt power supply and i want to use a video card, Forsa GeForce 6600GT 512MB DDR2 PCIe Video Card w/DVI TV-Out. i know its too little but i used it before i downgraded my vista to xp and it ran perfectly and smoothly for gaming with only 250W supply|||1st to start off does your mother board handel pci express and computers now comewith power supllies over 450 to 500 watts. plus using a video that requiress more power to run will shorten the life of the power supply . you really need to to make sure your computer can run that card. it does not matter what windows os u run. it does matter on the hardware u have |||the graphics card in question should run quite easly as long as you dont have too many other things connected to your powersupply at the same time but it is every easy to upgrade to another psu

Product Code: 04575

Description: Power Supply 550W Coolermaster eXtreme

Warranty: 12 month(s) RTB

Stock Status: Available

IT Estate Price: (Inc. GST) $69

this is the advertised price at IT ESTATE a great place to shop

why run the risk when its 70 dollars to upgrade|||use 450 or 500 W psu for good performances and long life.

psu problem can cause your mother board and video adapter.

capacitors can damaged by awful power supply.

and if psu can't generate more power can't start your pc by 250W psu.but it working check psu temperature (heat) .and it more hot you need change power supply(PSU)