Changed XP user name can't access share

I changed the user's name on a new Windows XP Pro computer to match a name of the old computer's user name that had permission on a network share. The new XP computer could not access the share. I noticed that only the name was changed, the user's folders were still under the original user name. I also found that I could still log into the XP computer with the original user name. Was the network user's name changed when the user name was changed? What name does XP use to log into the share, the original user name or the new user name? I finally deleted the user account and created a new user account with the same name and I was able to access the network share just fine. Apparently the changed user name was not the name that Xp was using to access the share. Is there a way to make XP log onto a share with a changed user's name or is it necessary to create a new user account?

Thanks,
Steve Smith