I thought I would start this thread to try and consolidate issues related to error 21, and also to post the problem I'm having with it.

I will add posts and responses that I find in my searches related to error 21 here as sort of an archive for all.
The problem I'm having:
I’m trying to set up my modded xbox so I can get Live latter and I’m getting the error 21.
I have an x2 pro chip, I’m running the X2 bios (I forgot the version but it boots evoxdash.xbe.) I have a 120gb hard drive (locked) and my xbox dashboard has NOT been upgraded to Live yet. My evox dashboard is “evoXdash.xbe” and the MS Dashboard is xboxdash.xbe both in the root of C.
When I boot with the modchip on all is well, evox boots and everything works. When I boot with it off I get error 21.
I’m kind of at a loss here, its seems I’ve done all I’m suppose to get the dual boot feature working, but well, 21 right?
I appreciate any responses up front, and apologize if this has been covered somewhere, but I couldn’t find it anywhere.
Thanks,
-Some dork