Wireless Connectivity Lost after Vista Upgrade

Greetings. A Comcast cable modem is plugged into a Linksys wireless router.
I have a home network with 2 computers, an HP Media Center running Vista and
a Thinkpad running XP. When the Media Center was running XP, the laptop had
no problems accessing the internet wirelessly. Since upgrading to Vista
(which involved a reformat of my hard drive) the Laptop cannot connect. The
Media Center PC can access the internet just fine. I have made no changes to
either the laptop or the router.

I noticed, after looking in the network connections area, that Vista was
able to "see" the wireless router (called it a gateway). Has Vista
commandeered the router somehow? If so, what settings do I need to change?
Or maybe it's impossible to network an XP computer with a Vista computer.
Any insight would be appreciated. I'm a beginner, but not a rank novice.
Thanks for your reply.