When I migrated from Novell NetWare 3.11 to Windows NT 4.0, one of my accounting programs didn’t run well in NT, so I set up a dual-boot with DOS—but DOS quit working recently. Now my bootsect.dos is corrupted and can’t be fixed.

A. When you install NT on a machine with an existing OS, NT Setup creates a file called bootsect.dos and copies the existing OS's boot sector, which resides in sector 0 of the C drive, into that file. Then, when you run the previous OS, NT copies bootsect.dos to the boot sector. Because NT Setup creates bootsect.dos, the file can be the boot sector for any previous OS and can be difficult—but not impossible—to recreate.

First, regenerate a boot sector for the previous OS (in your case, DOS). Make a 3.5" boot disk for your version of DOS, and copy sys.com from the DOS directory onto the 3.5" disk. Boot the troubled computer from the boot disk, and run the following command:

sys c:

This procedure will restore your DOS version. However, NT won't function.

You must now ascertain whether bootsect.dos exists on your hard disk; NT Setup won't overwrite an existing bootsect.dos file. Boot to DOS, and change the directory to DOS. Run the following command:

attrib -r -s -h c:bootsect.dos

If bootsect.dos exists, delete it. After you delete the file, or if the file doesn't exist, turn off the machine and remove the 3.5" boot disk. Insert the first NT Setup disk, and reboot the machine. At the first Setup screen, press the R key (for repair).

When Setup presents you with the list of optional repair tasks, select only the Verify boot files on your C: drive check box. When the repair process is done, you'll see a message that states Setup Repair is complete. You should then be able to boot to DOS and run your accounting program.