Adding 3rd computer to network - can't get Internet access

[Bobo Fett]

I've got a home network set up on a Linksys WRT54G broadband router, with DSL service.

I have my main computer working fine on the Internet. I have my Dell laptop connected to the wireless network fine, it shares files AND Internet access with no problems.

I have now added a third computer, a desktop, to the network. It shares files just fine, so it seems to be networked properly. However, I cannot get it to access the Internet.

I am running XP Pro SP2 on all computers. I have checked the Internet settings on the third computer via IE, they seem to be fine. I have gone in to my router settings and made sure the Internet Access restrictions are disabled, and I turned off the "Block Anonymous Internet Requests" setting for now to see if that helped. No dice. Not sure what I might be missing...any suggestions?