when was the manufactured date?
its highly likely that your specific console will not be able to downgrade.
even if your console can be downgraded, you need to buy a mod chip, and solder it to the motherboard, then take dumps of your nand and break the encryption of the cpu when you load back the downgraded image. and i dont think you are wanting to do that, since it takes a lot of time reading, and planning, including difficult soldering AND invalidating your 3 year warranty. to top it off, you wont be allowed on xbox live with an old dashboad, and there is the possibility that any new game you get wont be able to be played as it requires an update.
just get used to the NXE spam update. remember 360 games are meant to be played from CD, so smoe games will be benefited by copying to hard disk, and others wont. to be honest, you only see the dashboard when you turn the console on, not while your playing the game anyways.