Where - Software Update
Size - Unknown, can someone clarify.
The iMac G5 Sleep Light Update adjusts the brightness of your iMac G5 sleep indicator light so it's not as bright during the evening. The daytime brightness remains the same.
This update is installed in Applications > Utilities and should automatically launch. Click Update and follow the onscreen instructions to apply the update.
Note: Once the update has started, do not cancel or interrupt it. The updater takes over one minute to complete. During the update, your computer fans will run at full speed, but will return to normal once the update completes.