In Windows, removable hard drives are assigned drive letters on a first-come-first-serve basis. As such, a removable drive's drive letter today may not be its drive letter the next time it is attached.
Furthermore, the file path to a removable drive in Windows is different to its file path in Linux. Areca should handle this flawlessly.
Areca should try to find a repository in case its not found in the last known path. It should store the drive's label in its config and try to find the drive letter that has that label. If that fails, it should try all existing drive letters/mount points and check if that drive/mount point has the path that the repository uses.
For example if the repository was kown to exist in E:\Backups\MyBackup\, it should check for a Backups\MyBackup\ folder on all other existing writable drives (C:\Backups\MyBackup\, D:\Backups\MyBackup\, and so on).
Once found, it uses and stores that new path instead as the new repository path.
Further sanity checking may be useful (check if a valid .bcfg file exists in the new repository path, same target name, same sources, etc.).
As a last resort, if Areca still can't find it, the user is asked to type the repository's path.