There's more than one type of VPN. You want to make sure the firewall passes PPTP. PPTP uses GRE which is different from IPSec VPN's.
As for the shares, make sure your pc is on the same workgroup. Also take a look at Advanced Sharing Settings. They're under Control Panel => Network and Internet => Network and Sharing Center. It's a link on the left.
Network discovery should be on. You may need to change a few other settings such as File and Printer Sharing, Password Protected Sharing, etc.