Wireless adapter not working?

Hey guys. I built my first PC yesterday and I forgot to get a wireless adapter for it, as I don't have a cable connection in my room.
So I remembered my old Dell XPS 420 had a wireless adapter so I took that out and put it in, now I pick up a few connections, including my house one, but when try to connect it asks for the password, and then says it cannot connect.
I thought I might of damaged the componant, but I touched the chasis and used an anti static wristband so I doubt I did.
I double checked by putting the adapter back in the old PC, and sure enough it didn't work.

I installed some drivers off the Dell website and it suddenly began working. So it isn't damaged.
The Dell XPS 420 I got was Windows Vista 32bit, and my new build is Windows 7 64bit. However, I updated my XPS to Windows 7 a while ago and it's running on Windows 7 32, but the adapter works fine in it.
What could be the error that is stopping it working in my new computer?

How far away from the router is the other computer where the card is not working? Walls in between? Did you install the drivers for the card in the new computer?