only one version should be active. Whichever one you ran last. Old versions can simply be deleted (there is no specific uninstall)
If you are having trouble after deleting a version then you can clean out the registry settings. The best way is to use the mwgfx registry cleaner/editor from the front page of the site (under specials....). This will list all the registry entries for the various mwgfx programs on your system and let you edit or delete individual entries or the whole set for a selected program
