I am probably giving you too much information, but I am avoiding the real work I have to do today.
So I hope this helps...
After you do the wizard on XP make sure you have a hand icon under the folder you want your powerbook to access. If the folder you shared has a space in the name, right click it and go to the sharing tab. You should see the share name and the permissions button. I would remove the space just because it is easier.
Then on your Mac Finder go to Go and then Connect to server. If it doesn't see the XP machine you might have a networking problem.
<If you have a problem...>
Back on the PC open up a command prompt and then type ipconfig. This should tell your the IP address of your PC.
Back on the mac go to Applications, Utilities, and terminal. Then type the command (ping <your PC's IP> <return>) If you Mac doesn't get a reply from the PC, you have a networking problem....
If it does get a reply then the PC is having a problem broadcasting its info, and you can try this... Back on the Mac under Connect to Servers type the location like this... smb://<your PC's IP>/<Your PC's Share name> When you hit ok you should get a prompt for a user name and password. I usually find that on the Mac if you do not see the workgroup/domain filled in then the PC didn't respond. But if it does have that filled in on the password prompt then just type your username and password for the PC. (The Mac will fill in your username from your Mac, but this most likely won't be a valid name for the PC... )
Hope it helps!