Are you sure your ISP allows communication thru port 1723.
I spent a week wasting time making sure everything was correct, all settings good, router/firewall, GRE protocol 47 allowed on router and PC firewall.......you name it. At one point I disabled firewalls completely, ran DMZ on the VPN host machine as well did these same settings on the client PC.
There was no reason it shouldn't have worked, unless that port was being blocked somewhere else.
I phoned Telus and found out they specifically block the VPN port 1723.
I pretty much gave up at that point, other than paying to get an account with port 1723 unblocked.
As was suggested, you could use one of the "easy" style VPN 3rd party programs.
Probably the easiest way to get yourself at least running for now....until you figure out what is going on.