I decided I should have some way to reinstall the complete operating system if something happens when I'm far away from the internet. On Windows I would dig out the XP CD and reboot from it. On the XO computer you can create a boot SD card. See the instructions at:
Activated Upgrade - OLPC
I happened to have a 512M SD card so I cleaned it off and installed the files mentioned. I also added another text file with those instructions plus instructions how to reinstall everything I had on before. And I also put any critical programs like the Mariner .gz install file on the SD.
I actually tried it to make sure it works and it did. Its a good way to clean up the flash drive.
Beware: if you do it you will lose everything you had installed previously!
Paul