Have you installed the DFU drivers?
Tutorial: Installing DFU-Driver on Windows [24 Feb 2015]
and while you’re at it you can also install the USB Serial drivers
https://docs.particle.io/guide/getting-started/connect/photon/#installing-the-particle-driver
Just be aware, in Win10 you’ll find the Photon not under “Other Devices” but under “Ports COM/LPT” and your Photon needs to be out of DFU Mode - best in Listening Mode (blinking blue)