Ubuntu server 6.06 LTS won't start after install

Installed the OS from an install cd I burned.  It seemed to install fine, though it was unable to automatically configure the network.  I reboot the machine, it passes POST, it passes GRUB (will go into the GRUB bootloader if I choose), screen wipes and goes into the next phase of text output.  This goes pretty fast, but only about a third of the screen is filled before the entire machine reboots.  Rinse, lather, repeat.I'm a n00b, so I've no idea what to do with the rescue options of opening a shell in the install environment or elsewhere.Ran a bunch of hardware diagnostics on my machine, circa 1997 pentium box, and all passed.  Memtest86+, Eurosoft PC-check.What steps do I take from here to try and figure out what's going on, so it can be fixed?