Ten torture methods later, Winston (like all the other prisoners) confesses to a long range of crimes — espionage, sabotage, etc. The confessions are a mere formality. This is so not over yet.
Winston's spirit is broken (along with several body parts), and his sole concern becomes to 1) find out what they want him to confess, and 2) confess like crazy to avoid torture.
O'Brien is still running the torture show, by the way. Turns out, he's been surveying Winston for the last seven years. Or so he says.
Winston is strapped onto a torture machine that is designed to stretch backbones until they break.
O'Brien controls the dial that directs the machine. Suspense builds. So does the tension.
O'Brien informs Winston that his crime was refusing to accept the Party's control. Winston even went so far as to rely on his own memory.
Winston becomes brainwashed, as tends to happen when you're on a backbone-stretching machine.
O'Brien informs Winston that Julia has long betrayed him, quickly and easily. Winston, by now focused on the backbone-stretching machine, doesn't give a hoot.
You might be wondering why they do this whole torture business. Winston is too busy being tortured to wonder, but O'Brien tells him anyway, which is convenient for us. He says that they convert "traitors" before they kill them so that there are no martyrs.
Through many more paragraphs of prolonged torture, Winston relearns "doublethink" and eventually, "crimestop."