Just from a look around this seems like a pretty popular error. I've been googling for hours to solve this on my own and am now going to ask the experts, since I'm rather new.
Basically, I successfully modified 2 xboxes. The first XBOX I modified, I mounted via curlftpfs and like a true noob deleted the dash from the root and my save exploits are no longer loaded on the xbox hard drive. So I pull out the drive and connect it to my PC, set as a primary master (Had to disable auto detect tho) and it shows up fine under xbrowser and via the copy methods. I'm wondering if xboxhdm 2.2 is somehow corrupting the files as it transfers them over?
I do have an eeprom.bin backup, however. With this, I've run through the usual xboxhdm to restore the xbox with the retail dash and files. (Of course ensuring that all files are there.) I'm doing this via xboxhdm 2.2. I'm not attempting to upgrade my XBOX, I'm simply trying to get the original hard drive to boot either the original dash or a 3rd party dash.
HD is detected fine, unlocks fine, locks fine, *seems* to copy fine via a full wipe through xboxhd as well as a restore of C, however I still boot in to error 21. I've tried to do an update via splinter cell (The game I used to load krayzie 1.1.1 orginally) Even after the update, still error 21. If I try to copy the SC exploit files to UDATA and load the exploit in SC the game simply freezes up completely after hitting Check Points. I've tried wiping just to ensure something wasn't preventing the exploits from loading. The exploit is fresh and not copied from another exploit attempt.
I've tried installing the original files and then going the ndure route with core files, generic kernel and installer and what happens at that point is I won't boot to the error 21 screen but it instead will sit at the XBOX Logo with microsoft beneath it and will not load further. I've made sure that the eeprom serial matches the xbox and that all checks out fine, too.
I'm pretty much drawing a blank at this point.
Thanks for any help that you can give

Small Update: If I copy across the files to C: and E: after wiping them in Midnight Commander it boots to Error 13.
This post has been edited by Peanut76: Jul 28 2011, 07:35 AM