You cannot do this.
BootCamp/Windows must run on a partition on the main (internal) hard drive.
Move some stuff off the internal drive onto the external AND make a backup of it before you do.
Ok the long and short of it...
I have a Macbook Pro OS 10.5.8 160G HD with 7G of space.
I have an Ultra mini portable disk, Firewire, ATA 133 3.5", 250G.
I use to clone my Mac using SuperDuper for backup.
There is a program I must use in Windows.
I will need more space than I have left for the Bootcamp partition.
What I would like to do is have
an external HD that
runs Windows from Bootcamp
and have all the 'other' software and related files saved externally.
(I'm an artist not a techie - so layman's terms please.)