I guess one of the nice utility often forgotten that comes with Cisco VPN Client is SetMTU. It is installed with the client and you can find it at;

StartMenu->Programs->Cisco VPN Client->SetMTU

So it is a peaceful life and don’t have go through the GUid in registry finding out which adaptor you want to set it :-)

Oh yEAH! Using CVPN Client on Microsoft XP ? Don’t forget to get the latest version, 4.8 which is the stable one and you can download it from Cisco Site.