I could tell that the computer was booting up quite fine. After sitting awhile, I was able to make a backup of my home directory by waiting long enough to think that the desktop was up, alt+space to open tilda (a nice drop-down xterm-replacement), creating a backup tarball and scp-ing it to my ftp server.
(Note: I'm about to describe opening up part of a laptop. Trying to do something like this could damage your hardware, void your warranty, or kick your puppy. I'm not what you call a "trained professional", but while in college I did service and repair computers as a part-time job, so I've had experience in this area. Just use your noodle.)
After that, I found the T400 hardware replacement manual, and found how to access the backup battery next to the touchpad under the wrist rest. I disconnected the battery and turned on the computer. It went through a few tries of boot-up/shutdown-down before finally trying to post, but the display was working. I'm not sure exactly what the problem was, but it was fixed by pulling the battery and, in effect, resetting the bios options back to the factory default.
I reconnected everything, although I need to be careful with the screws. According to the hardware replacement manual:
Loose screws can cause a reliability problem. In the ThinkPad computer, this
problem is addressed with special nylon-coated screws that have the following
- They maintain tight connections.
- They do not easily come loose, even with shock or vibration.
- They are harder to tighten.
- Each one should be used only once.
So, suffice to say, I'm going to be looking to order some replacement screws, and if they're not too expensive, a torque screwdriver. I'd probably be ok with just using the old ones, since I don't rattle my laptop around too much, but I doubt the screws cost much anyway.
Turns out after playing with it some more that the issue is when I have the discrete (ATI) card activated (using the setting in the bios). I can now use the integrated card, but get no output on the screen if I try switching over to the ATI card. Looks like I'll have to send this guy in at some point.