It's simple to enter the NCK code in the Phone,you need to use the Instructions to enter the NCK code in the Sony Ericsson Xperia X10 phone,find in which Country ,Network it locked now?
Get the Unlock instructions from here
Onlinegsmunlock and Unlock it.....
Sony Ericsson Xperia X10 Unlocking Instructions
Warning : Do not enter any wrong unlock
codes on your Sony Ericsson Xperia X10 mobile phones. If you enter over a
certain amount of wrong unlock codes on your Sony Ericsson Xperia X10
mobile phone, your phone may get hard locked and sometimes become
unusable.
1. Switch ON your Sony Ericsson Xperia X10 with a
Not Allowed SIM Card.
2. Your Sony Ericsson Xperia X10 will request to enter an unlock code.
3. Tap the box where you have to input the code and a number pad will appear.
4. Type in the unlock code we send to you.
5. Press the 'Unlock' button on the phone.
6. Your Sony Ericsson Xperia X10 phone should now be unlocked.
*NOT ACCEPTED : We mean, to use a sim card from a network other than the network your Sony Ericsson Xperia X10 is locked to.
Each Sony Ericsson Xperia X10 mobile phone has an
unique unlock code. You can buy the unique unlock code for your Sony
Ericsson Xperia X10 mobile phone using the form above.