Was it actually a bad drive or bad cable? When looking at any old system first assume any flat ribbon ide cables will likely need replacement since those will get dried out, stiff, and no longer reliable.
The second item is making sure if ide the drive's jumper is set correctly for the position on the cable. With some prebuilds the cable select not master or no jumper at all is seen rather then setting a drive as master as you would on a custom build. That can throw you off fast.
The third item is a familiarity with the bios setup for the boot order and even a list of hard drives when highlighting that item with some bioses like Award, Phoenix, AMI, etc. there. If the cd rom option or floppy is set as first and a disk just happens to be left in a drive there's no boot information to find resulting in errors.
When setting the hard drive as first and only in the boot order you force the system to look at the hard drive first and only. Most old systems see floppy, cd rom, and then hard drive or cd rom then hard drive when no floppy is included on a prebuild.