OK, well, I’ve got Ubuntu working now. Here’s a few notes, in case they’re helpful to anyone else.
My machine is configured with one SATA drive and one older IDE drive. The SATA drive is my main drive, with Windows XP installed on it. I put Ubuntu on the IDE drive. The install went smoothly, but to get into Ubuntu, I had to go into my BIOS and change it so I’m now booting from the IDE drive rather than the SATA. The IDE drive now has GRUB on it, so that allows me to get into either Ubuntu or XP. And I customized GRUB to default to XP using Startup Manager, which I installed from the Add/Remove application, which is quite nice.
I’ve got an ATI video card, which worked fine by default, but of course I had to mess with it. I installed an ATI driver, then got the eye candy working using the method described here. It seems to be working OK.
I also installed a couple of other things that are pretty much necessary: The “Ubuntu Restricted Extras” package has the stuff you need to play MP3s and DVDs. And, for some reason, emacs isn’t installed by default, so you have to pull that down.