When i turn on my phone it asks me for the phone lock code

Go into ur phone settings, security settings, phone and sim. Scroll down to lock code.
To change the code to ur own, select it, and it will ask for the default lock code which is 12345. Once confirmed, it will ask u for ur new code which can be
4 or 5 digits. Pick something u wont forget. Then it will ask u to confirm it.
Done.
Now if ur phone has an autolock feature, u can set it by selecting it and selecting user defined and set a time, like 10 or 15 minutes, up to u. Ur phone will lock after
that set time of inactivity. U will still be able to take calls, but need to put the code in to do anything else. Code will be requested each time u turn ur phone on.
Depending on ur nokia, u may have remote lock feature. With this, u set a password, and if ur phone is stolen and ur worried that it hasnt autolocked, u can send that
password to ur phone from any other phone by sms and it locks it.
U may also have the feature to have the phone lock if the simcard is changed and u can enable that too.
Finally, u have pin lock. This locks ur sim card, even if a theif takes it out and puts it in another phone, the code will be required to use ur sim.
To change the pin code, its the same as the lock code change, but the default code u need to put in first is different. Its usually 00000 but if that doesnt work, select
cancel, and call ur service provider, they will give u their sim pin default code, and after uv done that, select pin request on, and it will ask for a code every time u
turn ur phone on.
Its a good idea to make ur pin and lock code the same so u just enter them consecutively on start up
Hope this helps. [answer taken from Yahoo.answers]

try this link. it may help you,
http://twilightwap.com/mobile/secrets.asp?phone=Nokiagoodluck

Ask your friend what the code is and if they do not know, ask them where they got it from because you won't be able to unlock it unless you restore the phone to factory settings and you can get that info at the erricson website.

default security code is the last 4 digits of your telephone number.

try 0000 or 12345 general codes to unlock if not send your IMEI number.

*#06# or
To By Pass SIM Lock:
Turn phone on then dial 112 call # send end send end. This work until the phone is turned off.

go to Sony Ericsson service center for a reset or call me 99999-16148

u have to unlock the code using software xs++

you have the prblm of lock code then whenever u restart ur mobile plz enter 0000 code. then ok. THANK U ITS FUN SONYERRICSSON HELPLINE 1800111800 for india.

Was the phone locked? Or the SIM card?
Because if the SIM card was locked then type in 3 times a wrong pin, then they'll ask you for a PUK code, call your service provider and ask them for your PUK code.
If the phone was locked- in other words, you put a pin to prevent people from using your phone by changing SIM cards- then I'm sorry I can't help you.