New SDRAM modules have been installed in the AMD Duron 1.3GHz system which now has the max. RAM for the board (1.5G). With only this change:

* OpenSolaris boots up, but it doesn't configure the Zyxel G302 wireless card or the onboard AC97 audio.
* Ubuntu hangs with a black screen and a white mouse pointer in the middle. The mouse pointer is frozen, but the keyboard has worked fine up until that point.
For a sanity check, trying my Toshiba Laptop with a 2.0 Pentium M chip and 1G of RAM. Another family member is using this system Monday thru Friday, so I can't take it over:
* OpenSolaris starts to boot, but hangs on a blue screen with the "OpenSolaris" logo in the lower right corner.
* Ubuntu just works! Wireless is configured, sound is configured. I plug in my Lexmark X4530 and it can't find a driver, but offers a screen to select a PPD file: I didn't have to do anything but plug it in.
Conclusion: Everything is a project. Since the goal is a Linux desktop at home, I'm trying for the path of least resistance. There is a wiki for debugging live cd and other Ubuntu boot problems, so I'll start there.