You are making a lot of confusion: you,
@jocke90s , keep calling this appendix PVR hardrive...
And you
@Mick, thinking he's referring to install the image not in flash but in the harddrive OF THE kit. He's not.
The PVR kit is... a kit, as of its name, meaning you can attach this kit (which has a HDD in it) and have a HDD in the Zero4K, too.
But the port where you attach the kit is the 2nd USB port of the same USB interface. The kit is connected to a port placed at the bottom of the Zero4K which is a normal USB port.
And every USB ports of every computers or motherboards is a bus with two ports. In Zero4K only one channel is connected to a normal USB connector. The other channel goes to this bottom connector.
So the PVR kit
does not connect its HDD by a SATA channel but by a USB one.
For instance, I didn't buy the kit but I used a male/male connector to use a normal motherboard cable.
But, jocke90s, in theory should not be necessary to disconnect the kit to flash by the normal port. I say "should not" because I haven't tried. But, even so, it's not a tragedy to disconnect it for a moment! After all, you'll immediately understand if the box is flashing (then from your USB stick in the normal USB port) or not.