Since Tony Hawk skateboarded in, just about every "extreme" sport has had an airing. This week, Ski-Doo snowmobiles (next week, stunt supermarket trolley racing?). If the idea of racing skisleds leaves you cold, at least it is done well here. The graphics are great, the several-thousand-break-husky-powered speed is exhilarating and handling the sleds takes skill. But like snow on rooftops, the fun's soon melted away.