Fairly straight forward on the internet connection sharing:
Vista: right-click on computer icon in taskbar (networking) > nework & sharing center> click on down arrow next to "printer sharing" and tick "turn on printer sharing" > click on down arrow next to " Network discovery" and tick "turn on network discovery" that should do it.
XP: My Network Places> View Network connections> right click "Local Area Connection"> Properties> tick all things in list in window> Advanced tab> Firewall settings> exceptions tab> tick File & Printer Sharing> tick UPnp Framework
You might have to set up your router, let me know what kind of router you have and I could try and help you out on that as well if you don't get automattically setup with a connection after the instructions above.
As for setting up folder sharing you will need to set up samba shares and users in samba and both OS's. I would like to be able to give you a straight instruction on how to do this as well, but I had a difficult time with it, and I would not be the correct person to get info from
Sorry. Just do some googleing and you should be able to get tons of info on it. I will try to set up a how-to on this when I get some time (not googleing, samba
).