Microsoft wants everyone to use its mobile operating system, and it has decided that the best way to do that is by giving it away for free, in this case to phone manufacturers. Which is why companies like Celkon, a small phone manufacturer based in Hyderabad, are able to make the Win 400, a Windows smartphone that costs just `3,729. Available in black and white, the phone has a 4-inch capacitive touchscreen and 4GB of internal storage that can be expanded up to 32GB. The back camera is 5 MP and the front 1.3 MP. The Dual-SIM phone runs Windows Phone 8.1 and comes with Microsoft services like Skype.