On a Windows/OS X/Linux machine, format an external USB hard drive (with enough space available to backup your current hard content) into the FAT32 file system.

Connect your formatted hard drive to the Playstation 3 through a USB port and power the console up.

Navigate the XMB to the 'Settings' menu and select 'System Settings'

Select the 'Backup Utility' function to create a backup of your data - this can take up to 2 hours if you have a lot of data on the PS3.