How would you reset your saves in the original Might and Magic. I know that it wouldn't do much functionally since quests can be repeated and characters created at any time, but the lord quests can't be re-done simply by creating a new party. I'm also not sure that things like the ruby whistle and gold key can be re-found by a new party. So, anyone have any idea on how to completely erase the data? Do I just need to delete all the files and re-install from gog? If so is there a way to re-install without ending up with 2 copes of MM2-6?

Try (back up first!) deleting Roster.dta. That's the file that saves information about your party. I suppose just renaming it will work (e.g. to RosterOLD.dta) too.