Prepare the XO computer
Follow these instructions for "unlocking" your XO. Warning: A "locked" (as shipped) XO will not boot from SD, so you must follow the directions here before continuing. When you apply for a developer key you will receive it in 24 hours; you may prepare the SD card before the key comes but you will not be able to boot from it till the machine is unlocked.
The G1G1 XO laptops are "locked" so the OS can't be messed with (by kids, presumably). They must be unlocked to boot from an SD card. Here's how.

1. First you should update your XO to the newest "stable build." Usually the "simple online update" method works if you can connect the XO to the internet. Be patient, it takes a very long time with no feedback on the computer. It isn't hung till it's sat there for more than two hours! Be sure the XO is plugged into a power outlet.
   Simple_online_update

   If the "Simple Online Update" fails, or if you can't connect to the internet with the OLPC, or if you have more than one XO machine to update, then try this method of copying the update files to a USB stick and installing from there onto the XO machine. You will need at least 600mb of free space on a USB stick to follow these instructions:
   Full re-install of OLPC System

   Note: this will wipe out everything on the XO's drive, so back up anything you want to keep first!!.

2. Then you need to request a developer key for the machine, following this:
   Getting a developer key for your running XO.
   If you have updated to the latest build, the link you need for the application should be in Browse, under Activities (top square link at the left side of the home page in Browse. Go all the way to the bottom of the Activities page; the very last line is "... apply for a developer key." This is a tiny download, and you don't even have to enter your email address; you just click a few times, then return 24 hrs later to the same link and follow directions to download it to your XO. The key is a small file called "develop.sig", in /security folder on the XO. If this method doesn't work, move up to the top of this web page and check out the Contents there; it offers several other ways to get a developer key if you can't connect your XO directly to the internet.
3. At this point, be sure to copy the security key to a safe place in case you ever need it again to reformat your XO. It can be found on the XO's internal drive in /security folder. Start Terminal activity; insert a USB stick to copy to. Type
    cd /media
    ls

   You should see an entry corresponding to your USB; the path to the USB is "/media/[name_of_USB_stick]". Now type in Terminal:

    cp /security/* /media/[name_of_USB_stick]/

   you will get a message about skipping a folder; this is OK.

4. After you have the developers key, restart your XO. You should notice a brief message: "Press ESC for boot options." Don't do so at this point, just watch and see what happens. You'll get a bunch of text messages rather than the pretty pictures...
5. OK, now restart the XO again and press ESC when it tells you to. You should see an "OK" prompt. Type
     disable-security
   at this OK prompt and press enter. This will permanently turn off security on your XO. You can read, on the Activation and developer keys webpage, how to re-enable security, but there is really no reason to do so, just leave it permanently off.
6. Now, just one more step. Continue to the next page to upgrade the XO to a newer firmware version; the firmware in the current release of Sugar (8.2) doesn't work as well with SD cards.