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?