can't access shared forders on vista computer through VPN

>I have a Vista Business at work and want to access its shared folders from
> home from a laptop that I bring home that runs WinXP Pro. There is a VPN
> connection to my work network. I can ping the Vista machine and even
> connect
> to it through Remote Desktop from home (I post this message being
> connected
> to the Vista machine).
> I can access the Vista machine from the same laptop when I am at work.
> In the network sharing center on the Vista machine everything is on except
> media sharing. The network type is private.
> If I disable the Windows Firewall I can connect from home, however I do
> not
> want to run in this mode.
>
> What changes to the Windows Firewall do I need to do (i.e. allow
> exceptions
> fopr some programs or set some rules) to gain access through to the shared
> files on the Vista machine?
>
> Thanks,
> Peter