VPN Problem

Hey guys. So here's another question. I have set up a vpn server, and I do have network shares on my network that someone would vpn into. So, I tried vpning in and it worked. Now when I try to map a network drive, that does not work. Any ideas why? I set permissions for the username to allow it to connect, and everything seems like it should work. I am not using any client, I am using microsoft's built in software to connect to a vpn. So in summary, vpn in works, but for some reason mapping network drives don't. Any help would be awesome. thanks!