I do believe the above poster is wrong, M$ tries to spread the updates... by any means possible, and make it virus-'like'. Well not really, only three ways to get an update anywho, xbox live, hdd swap, maybe even memory card, and one is only sometimes(i.e. download... cd burn and update). Take one of your friends hdd's from an updated xbox live console, and pop it onto your xbox, updates are stored secondary onto the hdd to spread the update to any xbox it's hooked up to.
So just grab another updated xbox 360's hdd, hook it up on yours... get the update that way.
I do believe it is even possible to get the spring update, because I've done the hdd method... ethernet disconnected, had kernel 4552, and put in an updated hdd with spring update kernel 5759, and it asked to apply a security update to system software, right at bootup, I didn't update that way, just went on live later and got it, I'M NOT 100% on this idea, so don't flame at me for it if it doesn't work.