ok dude make sure u got netbeui installed on all machines. if ya do kewl, next. make sure its actually being loaded on at bootup. go to ur xp machine that ur havin probs with. check the event viewer(start -> control panel -> admin tools -> event viewer). i have had probs with netbeui and xp. sometimes it just decides not to load. then all u do is uninstall it and reinstall it.
so, now that you are in the event viewer click system. now go click view and go to find. leave everything alone in the find dialog execpt for the description. enter netbeui. if see something like "service control manger" under the source column. double click it. read it. if it says something bout netbeui not loading the just uninstall and reinstall netbeui. if not, next.
i have a similar set up to u. i have an xp pro machine and my roomate has a 98se machine. with his 98 machine because he is using profiles, for himself and his girlfriend. now, when he tries to access my machine he does so with a user name. that username has to exist in the xp machine. so just create one. but, its has to be the same as his user name exactly the same. now go back to the admin tools and go to localy security policy. expand local policys and click user rights assignment. look for "access this computer from the network" double click it. now just put that user name in there.
if your still havein probs. uninstall netbeui from all machines, reboot all machines. install netbeui in all machines and reboot again.
also, are u using ics in any of the xp machines??? if you are might wanna check it out and go through all the settings.
anywayz man hope this helps.
oDin.