Please can someone help? I'm having problems with the screen tearing in Morrowind when connecting my MacBook Pro (running Windows 7 64 bit in Boot Camp) to my HDTV (connected via HDMI), I've tried forcing on v-sync in the Nvidia control panel which works fine when my HDTV is disconnected but when it is connected it doesn't seem do anything?

V-sync is the feature that is designed to prevent tearing, and generally does a good job of it. You may want to check and make sure you have v-sync on for the monitor that's running Morrowind (I can enable/disable it for each monitor on my system, IIRC). The fact that it works without the TV but not with suggests that it's specific to that monitor.
You may also try turning it on in MGE instead of the drivers, that will make sure it is applied to MW.