Thanks, ruymbeke. Although your solution wasn't what I originally had in mind, it works... almost. Being able to dual-boot to a HD iso image - easily updated, no CD required - without any change to the Windows MBR, in a way that I can easily edit myself from within Windows, is a big plus.

Using a password with grub will solve the granny problem. I'm not worried about hackers, rather I'm worried about the computer-illiterate getting into something they can't handle. (Do you think they would notice if it booted to Linux instead of Windows? No!)

While I was at it, I upgraded to Knoppix 3.8.2. Since I don't need all the capabilities, I didn't want to fool with some of the things that seem to have popped up in 3.9 and later.

One problem, and it is significant: (1) Old method, prior to using Grub from HD: Using a CD (even wtih poor man's install), when I reboot from Knoppix all is OK. After termination, I get the message from Knoppix to remove the CD, then hit ENTER. If I hit enter, the computer re-boots. It re-boots to Windows if I did remove the CD, or re-boots to Knoppix if I left the CD in. No problem. (2) But new method, using Grub boot from HD and Knoppix iso from HD, as described above: When I reboot from Knoppix, it hangs at the end of termination, just before the line that asks me to remove the CD. At this point, even with patience, nothing happens. Hitting ENTER does nothing except feed a line. If I use CTRL+ALT+DEL, then Knoppix responds with a few lines that seems to indicate it is trying to do something, but fails. The only way to re-boot is to manually turn the power off and on! This is not an improvement.

Is this fixable, via cheat code or (if necessary and understandable) by edits, including hexedit to iso file?