Originally Posted by wagon3rw
Let me see if I have this right, I have to go back and partition my internal drive which has windows, create a /boot directory and then install grub? maybe?
Boot code goes in one of two places--or both:
1. MBR of the first drive--ie the drive the BIOS goes to
2. "boot sector" of a partition. In this case, there must also be boot code somewhere else which point to this boot sector.
In your case, you can simply put GRUB in the MBR of your main disk and have it go to the USB for its files. This would mean that the USB had to be hooked up to boot anything. OR, you could put the GRUB files in a partition on the main disk (perhaps that's what you meant above?)
Simpler solution would be to put GRUB on a floppy--used only to boot the external USB.
Getting more off-topic: I would favor putting both OSes on the internal drive, and then using the USB for shared data.