Tried to move main Dropbox folder but now Dropbox seems confused

aeneas wrote:

However, multi-boot is still a problem.

And it always will be. Dropbox is not designed to work in a multi-boot environment, at least not in the way you're using it. Multi-boot is fine, as long as each OS has it's own installation of Dropbox, each with its own separate Dropbox folder. The Dropbox folder should not be shared between installations.

aeneas wrote:

Whatever I did seems to now cause the Dropbox running on some partitions to think they are running on a different device even though it is the same computer

Dropbox may say devices but what it really means is installations. If you have a multi-boot system with installations of Windows and each of those has its own installation of Dropbox, then Dropbox will see that as three separate devices. It has always been this way.

You can manage your linked "devices" from your Security page.

aeneas wrote:

... and for that matter the very same Dropbox folder.

This is just asking for problems. Each installation should have its own Dropbox folder. You shouldn't be sharing the Dropbox folder between installations. The database that Dropbox uses to track changes is located outside of the Dropbox folder. If changes are made in one instance of Dropbox, the other instances won't be aware of those changes and this could result in sync issues or even lost data.

This is especially true is you use Selective Sync. If you use Selective Sync to remove a folder in one instance, the other instances will just see it as a deleted folder and then sync that deletion, resulting in the folder being deleted from your account and all other devices.