What power supply will I need for my new card?

[astronomeric210]

Hey, a few years ago I bought a computer from Best Buy (I know, bad idea). Here is the comp: http://www1.dealtime.com/xPF-Hewlett-Packard-HP-Pavilion-TV-M7560N-Media-Center-Desktop-PC-AMD-Athlon-64-X2-Dual-Core-Processor-4200-2048-MB-R

The current graphics card I have now runs fine: http://www.newegg.com/Product/Product.aspx?Item=N82E16814150340

I would like to get this card, but I need to know what power supply I would need, how many watts. It says it needs 500 watts, but does that mean I need a 500 watt psu? Does that factor in say, the motherboard and other stuff?

Please help! Thanks!

 

[astronomeric210]

Whoops forgot to add the card i wanted to get here: http://www.newegg.com/Product/Product.aspx?Item=N82E16814150329