The idea of using the bootable CD that came with the thinkpad was a good one: it worked! This thinkpad came with its own bootable cd for restoring the windows software originally on the machine. This cd boots to a dos program, and you can escape to a dos prompt via F3. This DOS recovery program assigned the thinkpad's cd player to drive X:. From there, I was able to switch cd's, go into the /install directory on the debian cd, run install.bat, and on to the usual debian install, which proceeded without a hiccup. Thanks.
For what it's worth, XF86Setup configured this machine quite readily to 800x600 mode. Everything so far is working nicely (except for that poor winmodem, but that hardly counts). Mark
