[dnanian]

This is unusual, because I have Classic on this computer, as well as Tiger, and haven't lost either.

I'm also unable to find a "Classic Compatible" option in Disk Utility: do you mean install OS9 drivers?

In other words, are you trying to boot from OS9 or just get Classic back?

If just classic, you should be able to use the "Software Restore" Feature of your CDs to just put it on the drive... so, no cloning, erasing or anything else necessary...