Microsoft was giving away Intel Galileo board to developers who sign up for their new Windows on Devices program. Last month, Microsoft detailed the roll out of the program on their official blog. Microsoft has updated their website Windowsondevices.com with SDK document and examples.
Through this program we are introducing a new Windows Developer for IoT Portal, with documentation and examples to support the developer kits we are starting to ship in small batches. These developer kits include a Galileo board and preview Windows image that supports the standard Arduino Wiring API set and a subset of Win32 API. This Windows image does not yet support Galileo boards outside of our program.
If you received received one through the Windows Developer Program for IoT or If you have bought your own Intel Galileo, now you can update it to run Windows. The version of Microsoft Windows released for the Windows Developer Program for IoT requires an Intel Galileo Gen 1 with 1.0.2 firmware. Gen 2 of the Galileo is not supported by this release.
Read the step by step instructions here.