...for about the same price, you could almost certainly get something newer. The 5500 is about 8 years old, and might not be much of an upgrade from the likely newer built in graphics card. As for "converter", I think the question here is actually what slot he has on his motherboard. If it's an AGP slot, I have no idea what a 2.9 GHz CPU is doing in the computer, and if it's a PCIe slot I have no idea what you're thinking about getting a card that old for.
As for details on determining AGP vs PCIe, you should definitely peek at Wikipedia.
The latest graphics cards are the AMD 6000 series or the nvidia 500 series, it is thaught that betwean Q1 and Q2 next year that the (nvidia)600 and (amd)7000 series will be launched, which will undoubtedly be better than the graphics cards of today, weather you wait or buy now is your choice.
Use Tomshardware to check if a graphics card is any good, they hav comprehencive and extensive charts on the subject:
http://www.tomshardware.co.uk/charts...marks,123.html
http://www.tomshardware.co.uk/charts...amer,2671.html
the 5500 is beyond old.
my work pc has a 6600gt and it struggles to run toribash without shaders, purely because its old.
i had a 5700 in 2004/5 and it was nothing special.
most motherboards nowadays have onboards that would leave the 5500 in their dust.
but granted the pc in question isnt that great, but i would still look at an 8600gt rather.
unless he gets the 5500 for free, i cannot imagine why someone would buy that.
the AGP / PCi thing, well i dunno, the inno3d sites links regarding the 5500 dont even work anymore.
its more likely to be PCI tho, and im guessing thats what the motherboard supports aswell.