The Content Download Drive is the location that your plugin instruments, FX and Splice content is downloaded to.
On default, this will be the MPC's Internal drive (Internal)
We would advise changing this location to a removable drive, such as a SD card, USB/Hard drive or user-installed SSD (MPC Live, Live II, X, X SE and Key 61 only).
Using such drives are most preferred than the MPC's Internal Drive for storage management purposes.
To stop this error message, please insert and select a drive, then tap 'Change' to set this drive as your primary Content Download Drive.
Note: This drive will need to be connected to your MPC when activating and downloading plugins or Splice content:
Learn more about the Content Download Drive here: MPC Series | Managing Plugins : Akai Professional