[narvatu]

I´m spanish and my control panel is in spanish, so the options are similar to:
Control panel->shared folders
Select the folder to share via NFS
Button privileges->NFS privileges
Button create
Host IP: 192.168.1.*
OK

Of course, NFS service is enabled in panel control->win/mac/nfs->nfs service

By the way, I dont use NFS with XBMC (I use samba). The problem with samba is in Two Syabas popcornhour that dont see samba workgroup, not PC´s. With NFS solved the problem for now