Im not sure you will need ssh if your are VPN'ing into your machine and simply want to map a shared directory.
I'd try the following:
First when you are on the LAN (ie not remote VPN) see if you can see the share you want on the sme server and make sure you can map a drive letter to it and access files etc.
Then, when logged in remotely via VPN try opening an explorer window (ie file explorer not internet explorer) and in the address bar type in "\\192.168.1.1" where you replace the ip in my example with the lan ip of the sme box. If you are vpn'd in you should be able to access the sme box by its lan ip - you can check by pinging that address.
if this works you should see the samba shares (ie ibays, hoem directory) pop in in explorer - you can then map a drive letter to this.
Once you have got it working, you should be able to use a script on your xp box - something like:
"net use z: \\192.168.1.1\myshare"
Does this help?