Jan4,
Thanks for the suggestions. FYI, the version number for both the Plop floppy and hard disk is 5.0.12 (installer 0.10).
Yes, I've spent lots of time in SETUP, but if I can boot from floppy without any setup, just by selecting HDA2 or HDA3, and I can't do that from the installed Plop, doesn't that mean something is different between the two versions, even though they have the same number?
Selecting HDA2 on the floppy boots OS X Snow Leopard successfully, but selecting HDA2 from the Hard disk version gives me a blank screen with a blinking cursor. Selecting HDA3 on the floppy boots Windows 7 successfully, but selecting HDA3 from the hard disk version gets me to the "Starting Windows" screen, which freezes and turns black.
Now back to SETUP. I followed your instructions for making Profiles exactly and got exactly the same results as described above when I selected "OSX" (HDA2 above) or "Windows 7" (HDA3 above) after bringing them up on the screen by pressing "q". Then I booted the floppy and tried HDA2 and HDA3, both of which booted just fine. There's something different about the floppy and hard disk versions. Weird, huh?