It is always best to have a dedicated PC (not connected to the net and without any other software) for operating your CNC.
Mach3 will work just fine with Win7 32bit
Backup the following:-
XML(Profile) – This stores you’re settings for Mach3, if you lose it you will need to re-setup you’re ports and pins, motor tuning, etc.
Screensets
Macros/Brains
Mach1Lic.dat license file
Or perhaps make a backup copy of your complete Mach3 folder.
Install Mach 3 then copy (into the new Mach3 folder) your original .xml file and your Mach1Lic.dat license file. If you have any special screensets or brains then they need to be copied over as well (not forgetting the bitmap folder for the screensets).
Tweakie.