1.U need to drives to do this (usb and/or usb HDD),formated in fat32
2.Copy your F3 installer to your pendrive( I´ve used LIVE INSTALLER)
2.Start your xbox without de hdd,and with 2 pendrives inserted
3.Start the installer and choose USB,to install F3
4.After installation,turn off the xbox and insert your hdd,dont remove your usb drives.
5.After F3 loaded,go to NXE
6.Go to F3 installer and choose uninstall ( HDD will be marked and usb no)
7.Go to F3 then to NXE again.
8.Run the installer again and choose HDD to reinstall F3( remember you will lost all your database,u need to do everything again ).
9.DONE
Sorry for my grammar,I dont use google translator
PS: I dont know how the closed beta worked,but,I think dash 14xxx is the issue,I hope someone fix it.