Gaming how to change the output resolution?

[nin10do]

i went to my friends house and connected my x360 to his hd tv and set the rez to 1080p.

now i'm back home and i need to connect it to my 1650 by 1050p monitor. so now when i connect the xbox the monitor says rez not supported and the x360 doesn't automatically go down in rez :/

could someone give me step by step instructions on how to change rez as i have to do it blindly...

e.g. turn on console
press up on the dpad to go from xbox live to xbox game.
press right x number of times to get to settings
then ???

btw i have the new dash.

 

[Jiggah]

http://support.microsoft.com/kb/911059/

Here...