Bringing this thread to a close as I'm the OP:
1) Thanks to the people who actually provided help.
2) To the others, isn't one of the purposes of Linux to allow us to do
what we want, how we want, when we want? I have a preference to blank
hdd sectors with zeros before doing a new OS installation; I've done it
for years with DBAN, etc., on various operating systems. If you think
it's pointless, senseless or whatever else, fine, but FWIW, on the 20 GB
partition, it took all of 5 minutes using the dd command from an Ubuntu
Live CD. FIVE MINUTES. And I know the hdd is good as new and ready to
accept fresh data.
3) For anyone else who wants to do it, I wound up doing two things:
blanking the MBR with "dd if=/dev/zero of=/dev/sda bs=446 count=1" and
the hdd partition with "dd if=/dev/zero of=/dev/sda2 bs=1M".
Now, go ahead and judge me for blanking the MBR even though the
installation went perfectly and the MBR blank took less than 1 second. :)