I use 2 external harddrives (E and F) on my laptop. It seems that Lightroom switched these drives. The photomaps that Lightroom shows on dirve E are indicated with "?" Those maps are actually on drive F. The same switch is made with the maps on drive How can I restore this?
Using Windows, change the drive letters back to what they should be.
Whilst you are changing your drive letters, you may want to consider using letters lower down the list. Windows is less likely to change them.