If you set your home machine to AUTOMATIC IP, and then make the vpn connection to your global IP, things will be simpler.
If you successfully create the VPN connection, you can access the SME shared ibays using the command line from Xp
NET USE Z: \\local 10 IP of the ntserver\shared Ibay name
I'm assuming your server is in a different work group or domain, so XP Explorer may not show show the VPN resources.