Wirelessly posted (8700g: BlackBerry8700/4.1.0 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/100)
If the BB is locked, the new user can't go to to options.
Just enter a wrong password 10 times it will wipe the BB.
That alone will not work if the phone has an old user's IT Security policy in place. Wiping as described only removes the personal data such as email, calendar entries.
If there is a former security policy you will see it at Options, Security and look down at the services listed at the bottom.
There is additional info here on removing a security policy if you need, as well as wipe instructions.
http://www.blackberryfaq.com/index.php/Main_Page
Good luck!