I still think you are using a cannon to shoot a sparrow.

Some web pages and for that matter programs are designed to not be easily copied or captured. Might even be a specific FastStone Capture with Windows 10 problem.

Personally I won't update to Windows 10, so if this isn't some private stuff link me to it in a PM, and I can try. I have have before captured a LOT more than 3 pages with it.