The xml is a file that contains your config, it is in the main Mach3 folder. The name of it will depend on the name of the profile you are using so if you open Mach as normal and look lower right at the profile name you can then look for a file with that name and a xml file extension. You will likely need to rename for the forum to accept so right click it and copy then go to your desktop and right click a blank spot and choose paste, you can then right click it and rename, maybe Kym_A.xml would be a suitable name. You can then use the additional options button on the reply page to browse to the renamed file and attach it to the forum.
Hood