I've read the sticky theard about Internet Sharing but I don't understand.

I'm using Knoppix3.6, witch have Internet access, through my 1st network card.
Then I have a WinXP machine connected to my 2nd network card.

How do I make it so the XP machine can surf through Knoppix3.6??
I am new to Linux so explain in extreme detail plz

btw I cant even ping the XP machine (with all firewalls disabled)