I've added a USB stick and then went to settings and unmounted it as when it's mounted you can't format it..., then there's a format option, (yellow) so i have un-mounted both the usb and the HDD and it's now formatting them both (one at a time using the yellow format option......writing blocks etc. now....(i wasn't that bothered about what was on there for me any way mate, your theory might work if you don't want to loose what you have recorded).....still writing blocks for now.....tik tok tik tok