If your Xbox360 console is connected to Xbox LIVE (which it should), firing it up on 19 Jan 2011 would trigger an ‘system settings update’ which re-enables an old feature. According to this site:
Xbox LIVE Dashboard update:
On Wednesday, January 19th we will issue a mandatory dashboard update that (re) enables the ‘Boot to Disc’ option in the Xbox 360 dashboard. After you accept the update, you’ll be able to set the option to boot to the Xbox 360 dashboard OR directly to the game you have in the tray when you power up your console. This option can be found in the System Settings.
Additionally, on Thursday January 20th the Xbox.com team will ship an update that contains a small update to the Gamercards. We’ve updated the Gamercard look and feel a bit and removed gamerzone from the card. Other than that, the same amount of information is on the card.
Although it seems to be called ‘Boot to Disc’, that wasn’t the title I see on my dashboard. Move over to ‘System Settings’ and you will an option named ‘Autoplay’ and a choice to ‘Disable’ or ‘Enable’ it.
Is this feature useful? Well, if you’re the type who wanna straightaway play/resume a game which you stopped a few moments ago because you had to go to work/school/supermarket for some groceries, etc this feature is cool. It saves you a few seconds or minutes thinking what to play that afternoon/evening/night.
Personally, I prefer to disable it, because whenever I turn on the console, I like to do a little browsing of the Marketplace. Sometimes, I get invites to join in some multiplayer sessions, so being able to stay on the Dashboard is ideal for me. Moreover, I don’t have a habit of leaving game discs in the tray. I always put the disc back into its case after playing.