From your description, it appears that the wireless card has been installed properly.  To be sure, open the control panel and check the Device Manager for any error flags, usually seen as a triangle having an exclamation point on it.  If the card did not have a driver, I think you would be seeing another type of error.  Since the computer is complaining it can't attach to the SSID given, the card obviously sees the wireless access point. I realize you are certain that you have the pass key correct, but your description sounds very much like an error in the key entry.  This key is case sensitive; you must have the upper and lower case and any spaces exactly as the key was entered into the wireless access point or you can't connect.  Check for things such as having the All Caps function selected, or transposed characters. For further help I suggest you post to the Networking, Internet, Wireless forum.
I cannot go on the internet on my Dell Inspiron 530, and I use a TP-Link, TP-WN722N wireless adapter.  It originally had Vista, then I installed XP, now I installed windows 7, and it won't work. I have all of the latest drivers (for the adapter). I called customer support, they couldn't help. When I connect, and type my password (I did go on my router's website and double-check i had the password right), it says 'Windows is unable to connect to {SSiD]. I have tried tons of solutions, including checking the registry, re-installing drivers, deleting or adding network profiles, changing security encryption, all of that stuff. On my other computer, where I also installed windows 7, it worked fine. I have no antivirus, or anything at all really, because I literally installed the OS (32-bit, by the way) ten minutes ago, and it was a clean install. Specs: Dell Inspiron 530 Intel Core Duo [NAME].33 GHz 3.0 GB RAM Intel G33/G31 express chipset TP-Link TP-WN722N Network adapter Buffalo WHR-HP-G300N Router  That's all I know off the top of my head. Any ideas?
Can't install TP-Link tp-wn722n on windows 7, worked on XP