Probably you shut down Windows incorrectly so now it's locked. If you still have Windows installed, try to restart it. If not... well, i would just copy all files to another storage and format NTFS.
Afaik umu sets dlls based on game's ID. But what if i launch noname game from, let's say, itch.io? In this case wine GE adds some universal stuff for any game. Is it works the same for UMU?
I have anki decks that i don't use on everyday basis especially for that. You can spend from 2 seconds to hours on this.