simple DSL w/router and XP networking

I have DSL, I set up a Linksys 4-port router, I have a Dell running XP, and a Gateway running 2000, the Gateway connects and stays connected, however the XP will connect but then it disconnects but shows that it is enabled. Also, though I have shared everything on both machines I can only see the two computers, I can’t access them on either machine. What is going on here? is there a bell or whistle in XP I am over looking??