INT 2fH 4a11H BX=0006H: Unmount Dblspace Drive

                                                         Compatibility: 6.0+ 
 Expects: AX    4a11H (mux number)
          BX    0006H (DoubleSpace fn code)
          DL    compressed drive number to unmount (0=A, 1=B, etc.)
 Returns: AL    DoubleSpace API Error Code (00H=success)
    Info: This unmounts a compressed volume; severing the connection
          between a compressed volume and its drive ID.

          It's probably a bad idea to unmount an drive on which files are
          open (for instance), or anytime Windows is running.

See Also: DoubleSpace Overview
          DoubleSpace API
          INT 2fH: Multiplex Interrupt
          DOS Functions