1. Windows operates PCs. It should be optimized for the things, like gaming or design or music, that can only be done well absent the space and power constraints of phones/tablets. This market is shrinking, but you still have hundreds of millions of customers.
2. Phones and tablets are a new market, and should be a new division of MS. Its engineers and designers should be challenged to come up with original software or hardware that people will want to use, and then apply its immense resources to beat the competition.
3. Get rid of the monopoly mentality on which MS was built. Use a flamethrower, firing squads, packs of feral dogs, whatever is needed to weed out the people who think it’s a good thing that your customers are stuck with you no matter how poorly you do your job.