Just set up a profile for the new machine. If you start Mach from the Mach loader (Mach3.exe) you will see an option for a new profile, set this up with your new settings and name it appropriately. You can then start Mach from the loader and choose whichever profile you want.
You could also a new shortcut so you could start by double clicking on the Icon you want. All you need to do is copy the original shortcut and then right click on it and go to properties, you will then see the target as C:\Mach3\Mach3.exe /p Mach3Turn or whatever your original profile is, then just change the last part to the name of your new profile.
Hood