I've discovered that the Administration menu is hidden in GNOME on the XO-1.5 for the simple reason that there are no administration applications installed. It reveals itself once you install something that places an icon there.
For example, you can install Fedora's GUI installer via the command line. First, connect to the Internet, then open a terminal. I normally just press Ctrl+Alt+Neighbourhood-View to get a console. Type this command:
# yum install gnome-packagekit
Answer Yes to all the questions, and it will download and install the relevant packages. After it has finished, reboot.
If you aren't already in GNOME, switch to it. Click on the System menu at the top and you'll now see the Administration sub-menu.
In that menu, click "Add/Remove Software". You may need to be patient while it is loading and waiting for system processes. If it is doing something, it will be reported in the bottom-left corner, just above the Help button.
Once it's up and running, you can browse through the categories or use the search bar.
Sridhar Dhanapalan Technical Co-ordinator One Laptop per Child (OLPC) Australia p: +61 425 239 701 w: http://laptop.org.au