Alright, so, my friend wants a new graphics card on the cheap. He has an HP Pavilion a1410n, so it only has a single core socket 939 processor. I couldn't figure out the PSU, but I'm assuming that it's around 300~400W w/ 16A on the 12V rail.
Right now he's using the integrated graphics on his motherboard (nVidia GeForce 6150 LE), so pretty much anything, bottle necked or not, would be an upgrade.
His budget is $100, which could get him a really nice card, but wouldn't do as much as if he has a better processor.