This diskette must be virus free. Boot to this diskette. Highlight the appropriate drive and hit enter to select. If it does, that indicates that the proposed partition and the BPB seem to match. They must be the same as they were when the drive was originally partitioned.
Older versions have different structures.
Type the letter W . Return to previous menu. Keep returning until able to exit Disk Manager. Remove the diskette and reboot the system. Boot to a bootable DOS or Windows 95 diskette that is both virus free and of the same version of DOS as is currently loaded on the hard drive.