If you have a mod chip, boot up an autoinstaller and rename the evoxdash.xbe back to what it is supposed to be. That will get you back to where you were.
To change to XBMC as your dash, you need to do the following:
1) Rename the evoxdash.xbe to evox.xbe. FTP the contents of the XBMC folder to the C drive, you should see all the folders and the default.xbe in the C drive not c:\xbmc\.... Rename the default.xbe to evoxdash.xbe.
I don't really like this method, but it is used by a lot of people and it is pretty simple.
2) My preferred method. FTP the XBMC folder to the Apps folder on the E drive so you have E:\Apps\Xbmc.
Rename the Evoxdash.xbe to evox.xbe. FTP the SHORTCUT by TEAM XBMC.xbe to the C drive and rename it evoxdash.xbe. Create a text file named evoxdash.xbe. Inside you only need one line it is: E:\Apps\XBMC\default.xbe.
Reboot the Xbox and you should be running XBMC.
