"jimkunz@gmail.com" wrote:
> My question.. with no floppy drive on the computer, how can I 100%
> reset a hard drive back to square one?

Without floppy drive, you need a bootable CD.
See www.bootdisk.com.
There are many utilities that can make a bootable CD from bootable floppy
image.

> The drive works fine in other
> computers as long as it's not the main drive.

Possibly it can be also a bad cable, or controller failure.

Good luck,
--PA