All real good advice, however there are a couple of real easy checks that should be the first thing you do. First make sure it's seated in the slot good. Second, go into device properties and ensure it is enabled. Look at properties and you'll be able to see if it's a conflict as pwnag3 explains. If all is okay, uninstall it (delete). Reboot and be ready to install drivers if necessary. It will automatically recognize that the device exists and needs to be installed. If there is still no recognition, replace the card.