So heres the deal. I recently switched from T-Mo to ATT and picked up a Curve. So now I'm selling my old Unlocked Pearl to a friend, but I want to restore it to factory settings before I give it too him.
It probably will take 5 minutes at the most and then the phone will do a complete reset. It "should" do a complete wipe of the handheld but you may just want to double check first. I have had to do this several times when I get a new "BB" and have not had any issues with data not being deleted.