Is it possible to do a full HDD install (knoppix-installer) to a external USB hard drive and use it to boot from multiple machines?

Today I have a PMI on the disk which boots with GRUB without any problems on all machines I've tried so far. What I would like is to have a full install so I could for example edit something in the /etc/ folder and still use it on multiple machines.

Is this possible?

/w