As mentioned in the manual:
Step 2: Choose your preferred language from the list. This language will be used throughout the rest of the installation, and the 6000 MAS software will use this as the default language after installation.
Warning
The installation process formats and erases all attached hard drives. If you have multiple hard drives, be sure to back them up prior to starting the installation process.
See the part that says "all attached hard drives"? Guess you didn't RTFM huh?