First to remove the boot error.
Reboot on the System Commander\Partition Commander Boot Utility disk #1. At a:\ prompt, type: checkmbr /mbr <enter>

You will return to the a:\ prompt and the screen will indicate the master boot record was replaced while not updating the partition table.
Take the floppy out and reboot, you will boot directly into your operating system.

A Boot 3 error is usually an indication that your drive has become fragmented.
Please defrag your drive (run it overnight, it could take awhile).

After defraging your drive, choose Start->Programs->System Commander\Partition Commander->Utility Program\Console->Enable System Commander, to restore the Operating System Selection Menu.