well, if it's two 9800 cards for $99 that's a great deal, so long as your board is an SLI board, which I assume it is. If it's a 9800GX2 for $99 though, then it should work in your motherboard. You will need a better PSU for either though. Also, your CPU will hold the cards back. In fact, because of the CPU overhead from SLI you may actually get lower frame rates in many instances compared to using a single GPU, just so you know.
Probably better with a single card, although even that is probably going to be WAY overkill for your CPU.
You are pretty limited in what you can do with a 939 socket -- can't upgrade the CPU to a dual-core or anything that could keep up with a modern video card. You're also stuck on regular DDR RAM, which is going to hold you back as well. I honestly would not spend very much money on this machine and save it for a new one, because there's nothing that will make it fast enough.
If you need to hang on to this machine for a while, most I'd spend is $45 to get an HD 3650, which is about the max upgrade for that system.
i see... thanks very much for the help, i have another more recent machine but i dont like it much everything is onboard, i guess ill have to do as capt_taco said and stack money for a better machine, seriously thanks again guys
EDIT: quote"I assume you mean 9800GX2, for $99 ca" quote"If it's a 9800GX2 for $99 though" sorry for the misuderstanding, what i was looking at was one (BFG GeForce 9800 GT Video Card - 1024MB GDDR3, PCI Express 2.0, (2) Dual Link DVI, HDTV, VGA Support and i wanted 2) for 99$ca each
but as i was expecting it and good thing i checked with you guys the old fart wont take it XD