If you didn't install the nvidia Network Access Manager software when you installed the chipset drivers, then you don't have the firewall enabled (and even if you did install it, I think you still have to go in and turn it on, it doesn't just turn on automatically). But if you did install it, you can uninstall the Network Access Manager. If you just want to disable it but leave the software, you should be able to get to the NAM through the properties for the network adapter, I think on the Advanced tab, or I think it's also in Control Panel.