You need to close Afterburner,
Open MSIAfterburner.cfg file with notepad.exe
under section [ATIADLHAL]
find/add or replace UnofficialOverclockingEULA = and UnofficialOverclockingMode = 0 with :
UnofficialOverclockingEULA = I confirm that I am aware of unofficial overclocking limitations and fully understand that MSI will not provide me any support on it
UnofficialOverclockingMode = 1
restart MSIAfterburner after saving changes, and enjoy your OC up to 1000. (Don't do it though)
*donate any extra mined coins to:
1KBti6iZTH6ysxtAiBrafKJN9bP1R5UbeKEnjoy your new horsepower