The matrix bios are pretty easy to turn off, but oh wait... I have a modded HDD. So now what? Obviously the original will work, but I really don't want to have to swap it out every time I want to play live. Is there a technique to leave a modded HDD in the Xbox with the original bios?

Well slap my A$$ and call me Susan. The simple solution to this is to lock your HDD via opjose's tutorial found on www.xbox-scene.com.