Hey Iain,

About your friends MacBook2,1 you brought in last night...   
   
Basically if you want Linux Mint on it then following these instructions should work just fine (as it's based on Ubuntu anyway)... https://help.ubuntu.com/community/MactelSupportTeam/AppleIntelInstallation#Quick_Steps   
   
Highlights being...   
- Install the rEFIit! mac app
- Use the Disk Utility to shrink the filesystem of macOS so you've got some free space at the end
- Boot your Linux installer from USB pen or DVD and install into that space
- Reboot and pick it from the rEFIt boot loader

That link goes into the needed detail though, and generally it's the same process whether it's something Debian/Ubuntu based or not.

I've only ever done this on a more modern MacBook14,1 which has it's own problems but works well enough if you ignore the power usage issues and lack of audio!

I expect that MacBook2,1 will probably have everything working due it's age.

If anyone else has any experience doing this kind of thing, feel free to chime in.

-- 
Steven Maddox
Lantizia