Is there a way to setup Mach3 so that I can have two completely different machine profiles (all the settings for limits, stepper tuning, offsets, etc)?

I want to use it with a 4 axis mill and a 3 axis router bed, (not simultaneously).

IS there an easy way to do this?

Just make seperate profiles for each machine then on starting Mach you can choose which one you want to use.
Hood

IF you copy the shortcut on the desktop and change the PMach3Mill the to P"whatever" you can set up two icons on the screen. It is under the properties of the icon...