Re: Ubuntu.
I'm pretty sure this is a matter of configuration, but it's beyond my pay grade. There's probably a log of /dev/ which would tell you what exactly it is seeing (if anything), which could potentially give you an idea of what to do next. Linux is a bit different than Windows in that you can hot mount more than you can in Windows, so you don't necessarily need to reboot constantly to get it working. What driver did you try with? AMD drivers have historically been shit, but apparently the open source drivers are not bad (not terrific, but functional) now.
Looks like you would probably want to boot with the Intel GPU and switch to the external GPU after booting (I think you could write a script to do this automatically once you can get it working). If you boot with the Nvidia GPU, it may try to set SLI (which it will fail to do), and fail to boot altogether. In theory you could set the external GPU to be the primary graphics driver, but I don't know if there would be problems with that.
