# 6. Host PC Modifications & Portability

During use, a portable app is permitted to modify registry entries and files on the local drive, however the registry and local files must be returned to their pre-run state on exit. This may involve backing up and then restoring the settings for a local copy (in either the registry or APPDATA) of an application on start and exit. The portable app must continue to work (settings and preferences maintained, language selection maintained) as the drive letter changes as the device is moved between computers. The applications Most Recently Used (MRU) file list should continue working as well.