How to unlock Sony Ericsson Xperia arc S LT18a,when I forget my PIN or password and screen pattern lock
After five attempts to enter the PIN, password or pattern lock you set on your Sony Ericsson Xperia arc S LT18a, your device may require you to enter your Gmail address and Gmail account password to unlock your Sony Ericsson Xperia arc S LT18a (if you have previously associated your device with a Gmail account).
If you have multiple Gmail accounts you must use the email address and password for the account linked to your Sony Ericsson Xperia arc S LT18a: the details for any of your other Gmail accounts will not work.
If you have forgotten your Gmail address or Gmail account password please visit Gmail.com to go about getting a reminder of your Gmail address and a new password to use.
If you are unable to regain access to your Google account, or your device, then the Sony Ericsson Xperia arc S LT18a will need a software reset from an engineer to bypass the screen lock.