gregmcc
Honorary Master
http://blog.us.playstation.com/2010/03/28/ps3-firmware-v3-21-update/
I guess its due to the hack being used by Geohot
For those PS3 users who are currently using the “Other OS” feature but choose to install the system software update, to avoid data loss they first need to back-up any data stored within the hard drive partition used by the “Other OS,” as they will not be able to access that data following the update.
I guess its due to the hack being used by Geohot