[Q] Enable USB Debugging Mode topic

I have a nexus 7 tablet. It stopped working and freezes at the start up screen (coloured balls circling). I have tried restart and factory reset with no luck. So decided to flash the original settings using the skipsoft Nexus 7 toolkit. I managed to use this to install the drivers on my windows 7 laptop. However I am unable to enter developer options to enable USB Debugging because the screen is frozen.

Please can you tell me how I can do this on a tablet that is frozen. I am not an expert with android and although I have searched widely have come up with no solution.

Many thanks

Brooz