Can Office 2003 & 2007 co-exist?

I run a small in-house training facility, focusing on Office 2003 apps. I am excited about expanding my offerings to include Office 2007 but I am expecting a rather slow conversion period where I will have to teach both 2003 and 2007 classes. My question is this: any thoughts on the best way to get the two programs to co-exist on the machines (12) in my training lab? I have had suggestions including dual boot hard drives, external bootable USB hard drives or flash drives, and even running one of the programs from a server. Has anyone had any experience and/or success with these or any other options? I would appreciate any input.

amjack