Also eliminate partition table?
 

If do this:

dd if=/dev/zero of=/dev/hda1

have I zeroed the entire drive including the partition table?

hda1 is only the first partition, you would need to do the whole drive.

Single partition
 

So if I do the same command, but just use 'hda' have I nabbed everything on the entire disk, partition table included?

It should do.

Yup!
 

I formatted using Partition Magic, then used the dd command with just 'hda' and went back into Partition Magic and sure enough, there was nothing but unallocated space. Cool!