(Updated 20 Jan 2008–added “sudo ndiswrapper -m” step, and added a note about manual configuration)
(Updated again on 5 Mar 2008–clarified some steps in the instructions)
You can probably figure this out for yourself if you search the web diligently. In fact, here’s a nice overview. Here’s my method for getting my WPC54G wireless PC card working with WPA wireless security under Ubuntu Gutsy Gibbon (7.10). The computer I’m installing on is an old IBM T23.
It’s worth noting a few things up front. First, My WPC54G is labeled “Ver. 2” on the back. Many Linksys adapters come in multiple versions, and different versions tend to use different chipsets internally, so instructions for getting one version to work may not work for a different version.
Second, in my case the WPC54G worked out of the box with Ubuntu 7.10, until I tried to use WPA for my wireless encryption. Once I turned that on, the notebook basically turned into a brick. The solution, it turns out, is to use the WPC54G via ndiswrapper. It’s not as hard as it sounds or looks.