Sony Ericsson Xperia X1 Hard reset - With the Sony Ericsson Xperia X1 turned off, press and hold the VOLUME DOWN button, and then briefly press the POWER button Wait for the screen with the 3 Android images to appear, and then release the VOLUME DOWN button.

Sony Ericsson Xperia X1 soft reset

Press the RESET button which is located on the back side of the device.

Sony Ericsson Xperia X1 hard reset

Turn off the phone.
Hold down LEFT and Right SOFT buttons.
While holding down both SOFT buttons press POWER button for a few seconds.
Release POWER button. Then release SOFT keys.

Other method is the same as above, except Press The RESET button while holding down SOFT keys.