Function:   DiskFixed()

               DiskFixed can be used on DOS 3.10 and later.
               DiskFixed reports whether a disk is removable or
               not, handy to use in programs where you will not
               want to check for the availability of some files
               all the time.

   Syntax:     DiskFixed([<nDisk>]) --> lFixed

   Arguments:  <nDisk> is a number indicating a drive, 0 means
               Current drive, 1=A etc.., when Ommitted, Current
               drive is assumed.

   Returns:    A logical value, .t. when Fixed, .f. otherwise.

   Usage:      if .not. diskfixed()
                    Wait "Insert Disk and Press a key"
               Endif