Reg41 is NVM, if you copy/paste folders from your nuvi to backup then you don't have reg41 backup.
Look at link that angelo provide and also try GTM on different nuvi, but i am 100% that problem is only in your nuvi and GTM will work on different nuvi, if you didn't create this then you don't have reg41 and you will lose model number when you erase reg41.
p.s.
What nuvi do you have?