Hello McDougal, it might be worth trying to turn off "simple file sharing" on the XP pro machines first. This setting can cause problems with seeing other machines and sharing. http://support.microsoft.com/kb/304040
Also go into the Advanced sharing settings and make sure that you have password protected sharing turned off in both the Home-Work and the public file sharing windows. There are two windows under advanced sharing settings.
Next make sure that the time/date is the same on all your machines.
If none of that works then try this registry adjustment.
create or modify 32-bit DWORD: LocalAccountTokenFilterPolicy
set the value to: 1