Windows sometimes doesn't recognize the jj40. The easiest way of flashing a new layout is probably using [HIDBootFlash](http://vusb.wikidot.com/project:hidbootflash).
1. Go to Windows Device Manager and find the keyboard (plug it in while holding down `Backspace` (`Top Right Key`)). It can be found under Human Interface Devices or under Keyboards.
2. Go to properties and the Details tab to find the hardware ID. You want the VID and the PID (code after the underscore). Plug them into HIDBootFlash and hit Find Device.
3. Use `make jj40:<keymap-name>` to generate the .hex file in the qmk basis folder. Select the .hex file in HIDBootFlash and press Flash Device.
## Troubleshooting
1. Try plugging the board in while pressing `Backspace` (`Top Right Key`). This will force it