i have many friends who i only can recognize by the renamed i have done to them with this program, and i need to format my hard disk, which file/s should i save with that information for when i reinstall messenger plus?

Go to Plus! > Preferences and click the Save/Load link in the left bottom corner. Choose to export your preferences and make sure you're selecting to export contact specific information.

Go to the Messenger Plus! Preferences window (Plus! Preferences) and click the "Save/Load" link in the bottom left hand corner. Then select "Export my preferences to a data file" and hit next. On the next page select a file to export to and make sure the "Export contact specific information.." box is checked and hit next. Now backup the file you just exported and use the same method (except this time select "Import my preferences from a data file" instead) to load them

edit: hmm bit slow.. but i was more detailed =P