OpenEtna installation videos
Backup your data! (use software available from the market, or just sync with your google account, ...)Get your phone in fastboot mode:
Remove battery
Slide out the keyboard
Plug in USB connector (still with the battery removed)
Press SPACE (or SPACE+MENU for newer firmwares) just when you see the screen slightly light up, untill the fastboot text appears on the screen.
If you are unable to enter fastboot, your firmware may not support it. See section "Recover fastboot"
If you are flashing an 'OpenEtna' image for the first time, or if the ChangeLog says that you will have to do an wipe, issue the next commands (else skip this step). This will do something similar to a factory reset and remove all userdata. You can backup your apps and their data by the very fine app "Titanium Backup" (market). As root/admin, do:
fastboot -w
Flash the images. As root/admin, do:
fastboot flash boot boot-versionXX-.img
fastboot flash system system-versionYY-.img"
'via Blog this'