Xbe Shortcut Maker is a very neat utility useful for who wants to run XBMC as a default dashboard.
1. download it
2. create your xbe shorcut to your xbmc folder , for example f:\apps\xbmc\default.xbe
3. upload your xbe shorcut via ftp
4. rename your shorcut with a file name that your BIOS can boot.
5. smile, reboot and enjoy XBMC as the coolest dashboard
this is best way to keep your root xbox hd clean and avoid to duplicate xbe and config files.