Some users had problems with flashing new images with HDD attached. So if you have problems disconnect it. Otherwise shutdown the box, open the lid, connect the HDD and the rest is done depending on which you image you use in the menus of the image...Like Menu/Setup/System/Hard disk
i think some people have had issues with the hdd holding files belonging to black hole image which werent being erased during the flash upgrade.
i am new but i think the way to flash is to transfer vu+ solo file of new image to usb stick, switch off box, insert usb stick at front, power up then press blue circle on front display to start upgrade then box reboots automatically.
i had no problems but as i say i did read that some people were having issues and had to dis the hdd in order to get a clean re-flash.
hth