There are no exclamation marks in the device manager. In fact, when I install the drivers from the cd-rom (or manufacturer website), I can't even see the driver name in the device manager.
Just before the driver installs it says, "Windows SP1 has a USB 2.0 inbox driver. Do you want to install [card manufacturer] USB 2.0 driver?" I click yes of course, and nothing.

I took allenb's advice and uninstalled a device that was working and installed the card in place of it. At startup, the bios screen did display a little message saying the "EC-something-or-another was updated successfully" Still, windows found nothing.

I needed USB 2.0 ports for this wireless-g usb network adapter. I guess the card is just bad or something is wrong with my motherboard. Thanks everyone for the helpful replies!