I have an early 2007 Macbook Pro running 10.5 that I've recently set up on a KVM with my primary desktop system.

The problem I've run into is that I have a 20" 1680x1050 LCD, and OS X only provides options to mirror at the resolution of the built-in display or to span. Since the built-in display runs at 1440x900, this leads to running my LCD at non-native res and a fuzzy picture. There isn't any option that I can find to simply disable the built-in display entirely and run the external LCD at its native resolution.

I am aware of closed lid mode, but the MBP was disassembled while in storage for about 6 months (took it apart to pull the HDD) and the cable to the touchpad, which controls the sleep sensor was damaged, meaning closed lid mode won't work. I've looked into replacing the cable, but the cheapest I've been able to find it is $75-100, and I'm trying not to invest any more money into this computer as it also has a completely dead battery and a few other minor problems.

I've found the app SwitchResX which appears to allow you to do what I need, but it has a lot of functionality I don't need and a ~$20 registration charge attached to it.

An odd set of circumstances, I'm aware, but I was hoping somebody might know of an OS hack that would let me just disable the internal display and be done with it. :)