Why does NT say the drive is full when there is free disk space during the conversion of the file system during the installation on a previously partitioned drive?

Why does NT say the drive is full when there is free disk space during the conversion of the file system during the installation on a previously partitioned drive?

If the drive is too fragmented there may not be room for the system files. Windows NT will inform the user that the disk is full. Run DEFRAG, or backup and run FDISK and format, then attempt the installation again.