If it is anything like my D-Link or Netgear cards, you have to install the software BEFORE installing the card. That's because they need their own software, not the ones XP would assign.
Try physically removing the card, then removing the card using Control Panel. (Control Panel, system, hardware, Device Manager)
Then insert the Linksys CD and follow the directions.
Then, physically install the cards. (Of course, turn off computer first)
Then boot up.
Should be fine.