If you're like me and you'd prefer a little more detail than those directions provide, you can use my version below, which includes links to more detailed directions for most steps.
[Disclaimer: I don't know that this will work for everyone in all situations, but it's what worked for me.]
I used a working XO-1.5 laptop to connect to the bricked XO-1 laptop that won't boot. (If you don't have a second XO laptop, you may have to install Python on your computer and then you will need to be able to start Python to run the automated script. I do not cover how to do that in my directions,so see the OLPC directions.)
1. Make sure the working laptop is connected to the internet (Connecting an XO laptop to the Internet)
2. Start the Terminal Activity. (Terminal Activity, Using Terminal Activity)
If you don't see the Terminal icon on the Home View (Using the Home View), change from Circle View to List View, then scroll down until you find Terminal.
3. In Terminal, install "pyserial" by typing at the $ prompt:
sudo yum install -y pyserial
Wait for the installation process to complete. I have moderately slow internet, and this took 7 minutes. Several times it looked briefly like it was not doing anything, so be patient. When it's done, a bunch of stuff will scroll down the screen, ending with "Complete!" and a new $ prompt.
4. Download and install the automated repair script "d6.py" by typing at the $ prompt:
wget --timestamping http://dev.laptop.org/~rsmith/d6.py
This is quick. Stuff scrolls down the screen, ending with "d6.py saved."
5. Disassemble the top of the XO laptop to expose the motherboard. OLPC has very good directions for this step, so rather than duplicating what they've done here, just go to Disassemble XO laptop to reach motherboard and follow their instructions.
6. Connect the serial adapter to the bricked XO and the working computer. Again, use the very good OLPC directions at Hooking up and using the serial adapter.
7. On the working computer, type at the $ prompt:
8. When the screen on the working laptop prompts you, turn on the bricked XO.
9. When it's done, the bricked XO will boot and the script will prompt you to press ctrl-c on the original working XO to disengage the two laptops.
10. Disconnect the serial adapter from the previously bricked XO.
11. If you've got more than one bricked XO laptop, leave the serial adapter connected to the working laptop and start over at Step 5 with the next bricked XO.