I seem to be having video mode problems during and immediately after setup.
As soon as my BIOS screen disappears and the Installation DVD boots, my monitor says "Video Mode Not Supported." After several boot attempts with the same result, I decided to just leave it alone for a while.
Lo and behold, when I returned, I found a setup screen waiting for me. After confirming that I'll my drives will be wiped and entring my product key and stepping through the few additional questions, it started installing. I left it alone again while it ran.
This time when I came back, I found the "Video Mode Not Supported" message on my monitor again. I think setup has completed, because there's now a new machine named "SERVER" on my network. But I can't see the console to know what's going on.
This exact hardware configuration (including monitor) was previously running Windows XP Professional without any issues, so I thought it would qualify as a "compatible monitor." I guess I'll try dragging out a different monitor and connecting it (not easy since my server is located in a somewhat tight space, but I'll give it a try).
What kind of esoteric video mode is WHS using?
Answering my own question: It appears to be using 1024x768, 32-bit color, which evidently was too much for my cheap LCD monitor to handle.
I temporarily connected a CRT and used Display Control Panel to change to 800x600, and now my LCD is happy.
I suggest changing WHS to use 800x600 as its default, as that's more likely to be compatible with even low-end displays.