How do I hook up a Linux computer to the internet using an XP host?

I am running Fedora Core 5 on my laptop and I have Windows XP Media Center on my desktop which is connected to the internet via LAN. I want to know how I can connect to the internet from my laptop using my desktop’s net connection. I already have all the physical connections set up (network adapters and cable) and I’m already using my network for file sharing. Please don’t offer any suggestions on using Linux as host (I already know how much safer it is). I want help on dealing with situation as it.

Incidentally, I’m also facing trouble using ICS from my XP partition on the laptop. It used to work flawlessly before, but I think after I installed Fedora it stopped working (although file and printer sharing areOK). I ran the ICS wizard again on each comp, but it didn’t work. Any suggestions on what might cause that?