Have you got a manual with the machine Reece? should explain in there - from memory I think you go in test as normal, scroll through to option test 10.3 - to get to this hold down the 4th button from right (4th along from START) while scrolling through the options (keep it held to get to the extended menus). You have only 5 seconds from getting to the menu to do it - refill key has to be turned then the HOLD buttons illuminate and you have to press them in order right to left. This could be machine specific but give it a go! It will say NVR CLEARED when done. turn refill key off and should be done.