Quick pptp question

5900 is real VNC, 3389 remote desktop. As long as traffic on those ports are allowed through the tunnel, you should be able to connect, barring any restrictive access lists.

What are the errors you are receiving when using the above applications?

i can't connect. I meant I couldn't connect via rdp. It doesn't work when i just put the computer name in the field for rdp.

Have you tried the ip address of the machine? If you connect via ip address, then the problems is dns configuration with your vpn deployment. For a quick fix, you can add a hosts file entry on the remote machine mapping your dns servers, domain controllers and file servers so you can access internal lan hosts via hostname to reach network shares, rdp, real vnc, internal websites, etc. Can you ping the host via its internal ip from your remote machine?

that's the problem, I don't have the dns, just the pc name.

not dns, ip address.

have you tried pinging other hosts by name from a command prompt, including the machine you want to access? It just might give you an ip address.

If you don't have the IP of the machine to which you want to connect, or the DNS or WINS servers so that you can configure name resolution, there is no way to connect to the machine. You are on a different network so the name cannot be resolved without DNS, WINS, or LMHosts files. If you do have that information you can see my blog as to how to configure name resolution with the VPN client:
http://msmvps.com/blogs/robwill/archive/2008/05/10/vpn-client-name-resolution.aspx