When purchasing a used BLACKBERRY on eBay, buyers often receive a minor shock when they receive their new phone. Upon turning it on, they get a message stating that the BLACKBERRY is locked and they need to enter a password. Not knowing the password, panic sets in. Fortunately, this is only a side effect of clearing the previous owner's data and is easily remedied.
What you do is simple.
Enter a new password, like QQQQQ. Enter it five times in a row; you will then be prompted to type in the word BLACKBERRY. Do this and then enter QQQQQ three more times. you will then be prompted to type in the word BLACKBERRY again. Do this, and type in QQQQQ two more times. On the last try, it will warn you its the last attempt. Go ahead and enter it again, and wait for the blackberry to reset. You will then be prompted to select a new password.
This is also an effective means of accessing your blackberry if you forget your password, although the downside is all the data will be cleared.
Hope this helps!
...read the full guide with pics here