A PPTP dialup VPN connection by default restricts access to internet. This may cause issues while the connected user wants to access internet while connected to internal network @ work. Domain member computers with proper firewall clients installed will allow the users to access through the firewall, however the user will notice the slowness immediately.
Here is a work around to deal with this situation. Please follow the navigation as follows and make changes to your PPTP dialup connection properties:
Navigation: Right click the VPN connection->Networking tab->Internet Protocol->Advanced
Under IP settings tab, uncheck “Use default gateway on remote desktop” selection box.
Users with ISA/TMG client installed must exit the firewall client prior making the VPN connection! in order to enjoy the native internet connection bandwidth.
Now try to connect to your PPTP VPN network and you should able to browse using your internet connection while you are connected the VPN network with full throttle.