So if I have this right, the current setup is this :
Win7 client / iphone -> "the Internet" -> Win7 PPTP server -> internal LAN resources
Currently, the above setup works in that both the Win7 client and iphone can connect to Win7 PPTP server
and the resource(s) behind it without issue. What you want it to do is force any internet traffic from the
Win7 client and iphone THROUGH the Win7 PPTP server as well?
Can you post screenshots of your complete PPTP config on both ends as well?