Here is the instructions I got off Morden -
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To downgrade your dash, you need to get the slayers disk. Search for a guy named slayer on this forum and follow the instructions in his sig to get the iso.
Use an xiso extractor to extract the iso to a temp folder. SimpleX and craxation will not work, try something else.
Now you need to delete some stuff on C:. Alternativly, you may just want to rename the folders and files instead of deleting them, you can delete them once you know the new one works.
Ftp into the XBox.
Delete:
C:Audio
C:Fonts
C:xodash
C:xboxdashdata.xxxxxxx
C:xboxdash.xbe
DO NOT REBOOT THE XBOX AFTER DOING THIS!
FTP the SYSTEMALLc folder from the extracted slayers to the xbox C:.
Check that all files sent correctly.
Reboot the xbox.
Then check your dash version, it should be 4920.
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Dave