Photon can only enter DFU mode with D7 dimly lit, unable to enter other mode

[ScruffR]

Photon in DFU Mode should not be listed as Universal Serial Bus Device.
In order to use it in DFU Mode you need to install the DFU drivers via zadig as shown here

Tutorial: Installing DFU-Driver on Windows [24 Feb 2015]

So it seems like some owners want to go slightly advanced but instructions for installing the DFU-driver is a little vague. How to put your core in DFU-mode Press on BOTH buttons Release only the Reset button Release the Mode button once the core start blinking yellow This will be the dfu-mode Pre-check! If you have somehow done this process previously but is unable to use dfu-util successfully, you will need to uninstall the DFU-driver 1st Put your core in DFU-mode Ope…

But as it seems you don't even have dfu-util installed, so I'd recommend to uninstall CLI and install the full package with this
https://binaries.particle.io/cli/installer/windows/ParticleCLISetup.exe