Ok so I was told to buy a new power source for my NVIDIA Graphics Card because I only had 250w.
I bought one with 500w.
I think thats more then enough, but I think I saw an artifact Im kind of scared to play my games because I will be sick to my stomach if I see this problem happening again. Its been almost 5 months, 5 MONTHS!!!:!:

Please tell me if this is enough power or if there is something esle I must do to keep this dreaded flashy crap away for good...

You may have to purchase an aftermarket cooler/heatsink for your card. The ones they put "stock" on cards are not very efficient, and are loud.

where can I buy one in a store, can I, like bestbuy or circuit city or something?
Are they expensive, are they hard to install?
Please answer!!

I would find them hard to get at a retail store like bestbuy or circuit city, and they really mark up prices on things like this. You can buy them from retailers like newegg.com and tigerdirect.com for a great savings.

http://www.newegg.com/Product/Produc...82E16835118117

I recomend this one for you. I have it installed on my 6600gt. Some people found it difficult to install the included ram sinks on the 6600 series agp cards, but if you do just dont put them on. The copper cooler was fairly easy to put on. I took my time and followed the detailed instructions and it was pretty easy. (unscrew your old heatsink off of the card, clean the thermal paste off of the gpu, install the retention bracket, reapply new thermal paste, screw down heatsink.) It is really quiet too. You will just need an open pci slot directly below your graphics card to make clearence for the cooler.