I'm not sure what you mean by creating a new group for users. If you mean that you would want to exclude some and allow other users, you would do that in smb.conf with:
"valid users = user1 user4 user5 ...".
Craig wants to share folders between Linux and Win2k. To do this without Samba he would need to use nmb (nfs). While nfs, is built in to Linux, since it is open source, you have to purchase it for Windows.
IOW, it isn't free. The most popular client is Hummingbird http://www.hummingbird.com/products/nc/nfs
To share a folder between Linux machines, all you have to do is right click on the folder (not on the desktop, but in your home directory). Click on properties and go to the tab marked "Local Net Sharing". Click on "shared" and then click on "Configure File Sharing".
Then it's on to "Allow all users" or "Custom" and you're set. But this only works between Linux machines.
Since I don't want to buy server software just for my Notebook, I just use Samba, since it's already there.