Just a quick note and I have to run. Domestic issues.
Have him make a small /boot partition on the first hard drive, so it doesn't use his windows space, and put swap and / (root) on the external drive, /home too if you think it is appropriate.
Install grub into mbr pointing to the /boot partition. After install copy "/etc/grub/message.mint"into "/boot/grub". Change the line "gfxmenu=/etc/grub/message.mint" in "/boot/grub/menu.lst" to "gfxmenu=/grub/message.mint".
This will allow the boot screen to work even if the external hard drive isn't attached.
Silverwingsketcher, don't worry, muskratmx will fix you up.
Gota Go... Good luck,
Fred