How to reset PIN for blackjack 2

[Guest porto35]

I bought a Blackjack 2 from Craigslist and was not aware that the previous owner set the PIN for that phone. When I put my SIM card in, the message shown that:"this phone can only be used with a specific SIM. Enter the unlock code or insert an approved SIM"

The previous owner totally forgot the PIN, I tried to hard reset by UP and POWER ON to format the phone but it does not work. Anybody can help me, please

Edited January 1, 2009 by porto35