Well, trying to upgrade from the DVD didn't work, either. It says I don't have enough disk space, which is ridiculous. But possibly my failed yum upgrade installation did something weird.
OK, so try a full install, but do a custom disk reformat, keeping untouched the /home partition that has all of my data on it. (All backed up, of course, so it's not a total disaster if I lose it.)
That seems to work, but then comes a screen asking me what kind of packages I want to use on this computer. I chose "Office and Productivity" and "Software Development," and then clicked the radio button that says "Customize Now," meaning that I want to go through the list of packages to be installed, add things I think I'll need, and subtract things I know I'll never use.
About 15 minutes ago I hit the Next button. The DVD spun for a few minutes. Since then nothing has happened.
I'll give it until after dinner or Doctor Who, whichever comes first. If I still don't have any response I'll try a full install, reformatting the whole fraking disk.
If that doesn't work I'll try something like Ubuntu.