Caution: Upgrading from Windows 8 Release Preview to Windows 8
If you wish to upgrade your existing Windows 8 RP to Windows 8 RTM or final versions, you need to be careful. Make sure you have backup of everything you need (software and applications).
I upgraded to Windows 8 from Release Preview and my previous installed software are gone.
However, your personal files like photos may still be there but I would not take any risk.