Puttin in a strong video card with low watt comptuer?

im trying to put on this video card

http://www.newegg.com/Product/Product.aspx?Item=N82E16814102843



but only on 250watt. im trying to see if it will work. if it attatch it on and if doesnt, wat will happen to my cpu?|||It will slowly kill your computer.



Cheers