Thank you for all the replies. I managed to solve my problem. Here is what I did (detailed, in case anyone else has the same problem):
1. I moved my computer to a location where I could connect it to the internet with a cable.
2. Windows automatically detected the wired connection and allowed me to go on the net.
3. I right-clicked "My Computer", selected "Properties", then selected "Device Manager".
4. Under "Other devices" I located my Linksys adapter.
5. Double-clicked the Linksys adapter.
6. Clicked "Update driver".
7. Selected "Search for drivers online" (or something like that).
8. Windows found drivers and installed them for me.
9. Disconnect the network cable.
10. Insert Linksys adapter.
11. Now it worked.
Thanks again for the replies.