I believe "\\Ubuntu\Lacie" is showing the share name, and not the path, but I may be wrong as I am still learning.
When you add users in Samba, I think you should have the same userid and same password that is used in your XP (Don't know about 98, but it could be same). That is how I set it up, and now it is working.
The "how-to" does give an option of what to do if Ubuntu is WINS and what to do if it is not, so I guess that is not mandatory.
Hope this helps. Remember, I am as new as you, but just got lucky and got it working by following the how-to.