Hard Reset Sony Ericsson Xperia X8

First, try this:

•     From the main home screen, tap menu
•     Tap Settings, then Privacy
•     Tap Factory data reset
•     Tap Reset phone
•     Enter your password if required, then tap Erase everything to confirm

If that doesn't work, or if your phone is frozen:

•     Turn the power off. If your Sony Ericsson Xperia X10 is frozen, pull the battery out and reinsert it
•     Hold the Left and right buttons located beneath the display
•     Press and release the Power button
•     Follow the on-screen instructions to hard reset your Xperia X10

All data including third-party applications will be deleted from the Sony Ericsson Xperia X8. Once the wipe is complete, the phone will reboot to its factory fresh state.