Spin to Win was a mystical 'Wheel of Fortune' game invented by magician Lee DeMarco, owner of the Tropicana casino.
After meeting the empathic demon Lorne, who was able to read peoples' destinies when they sang, DeMarco used him to determine which guests to his show had particularly worthwhile destinies.
After the more interesting destinies had been identified- such as Vivian, a girl who would go on to own a successful chain of restaurants in future-, the people were given a chip to play in the game, the chip was 'imprinted' with their destiny and taken into the machine, subsequently being stored in a glass globe before being sold on a demonic black market for a high price. The people whose destinies had been stolen were left to wander aimlessly through the Tropicano casino, playing slot machines that were rigged to never pay up, remembering their past but virtually unable to do anything more than what was in front of them due to their new lack of purpose (Although Angel showed some initiative when his friends were in danger despite his lack of destiny).
The machine was destroyed by Angel, Gunn, Fred and Lorne after the rest of the team came to visit/rescue Lorne in Vegas.