If you do decide to get it, do as you would do with any type of hardware you buy: Go to the manufacturer's website and download the latest driver set for the card. If it works with 8, it should work with 9, just make sure things get updated.
Oh and will, my mobo has 2 agp slots.

Also, from the way Myrthe is talking, it seems they don't have any vid card, save the on board one, in which case this one would be an improvement.
Now as you said (Myrthe) the clock speed might be a bit slow, but unfortunately, going with PCI, thats about as good as you can get, same way with the Pipelines, which is a major factor in speed as well. Since I have some free time, I'll look around abit and see what I can find.

If you're set on an ATI....
1)
http://www.newegg.com/Product/Product.asp?Item=N82E168141031672)
http://www.newegg.com/Product/Product.asp?Item=N82E168141025333)
http://www.newegg.com/Product/Product.asp?Item=N82E16814241020One of those would probably be your best bet, keep in mind the first two are cooled by heatsink only, so if you got either of those two, you would want to make sure that there is proper airflow through the case and by the card, as in no other cards close to it, or the card may run a bit hot.
Now on the NVidia Side....
1)
http://www.newegg.com/Product/Product.asp?Item=N82E168141430592)
http://www.newegg.com/Product/Product.asp?Item=N82E16814133007If I were you, I'd put my money on #1 for Nvidia. Faster clock speed, same pipes, better cooling system, same memerory clock speed, about the same price. And as I said earlier, from hands on experience, I've found Nvida to do a better job at driversupport as well. Ultimately, the end decision is yours.
Hope this helps.
Edit: oh, and as much as it wouldn't surprise me that your motherboard doesn't have an AGP slot on it, if you havent looked, see or post what your motherboard is and we can do some research to see if it has one, or you can do it yourself, as, as it has been stated previously, going with an AGP type card would allow you to expand your options quite a bit.