netbui is so annoying and slow... i wouldnt suggest it.

check your shares and turn your firewall back on. if your router can use ipx/spx, use it... it is safer than tcp/ip in that most attackers will try for that...

i'm not exactly sure how to do it with XP, but i belive....
right click on the folder you want to share... share it, set permissions as to what user can access what.... that should work.