.sum files are mapupdate related, can be deleted.
if the gmapprom.img and gmapsupp.img cover the same area nuvi wont see one of these maps.
You cant have the same City Navigator maps even if they are different versions at the same time in device.
gmapbmap.img is your basemap, don't delete.
gmap3d.img is 3D buildings map and must be the same version of your CN to show up and must be unlocked.
gmapprom.gma, gmapprom.unl are your preloaded map unlock codes, backup them in pc and remove them along the gmapprom.img