I see XP drivers for your system at the Acer site. I think you need to put those thoughts behind you. It's human nature to sometimes get fixated on the forest and not see the trees.
The driver configurations are different for every NIC manufacturer out there. I guess Nvidia has theirs locked down pretty tight. I'm sorry you don't see the same choices I see with mine.
If you have a friend or relative that has a laptop you could connect hard wired, I think it would be interesting to see what kind of speeds you get out of it. I suggest a laptop because it's easily transportable. It would be far easier than hauling the components of a desktop computer into your house. This would be a test of your modem and your ISP's infrastructure. I want to very emphatically stress the importance of hard-wiring directly to your modem. A wireless signal by it's very nature is potentially too unreliable to get an accurate assesment of what's going on. If you’re seeing slow speeds on another computer, I’d be on the phone with them demanding they fix their problem.
I like the advice from nsaspook. NIC's are cheap, but I would rather see you work the problem from the beginning. You've replaced the wiring (the middle), you've been messing around with the computer (the end). Make the assumption that your ISP is not blowing smoke up your behind and attach a laptop hard wired directly to your modem (the beginning). If you're still seeing slow speeds, jump on them big time. They pick the path of least resistance. It costs them money to fix problems.
If your problem still exists, then an NIC card may be your best next step. The card nsaspook linked to is for a PCIe slot. You’ll want to make sure that you have that kind of slot available. Your computer may have only the older PCI slot available. Make sure you get what you need for your system before dropping the money on it.
