Hi Fullzero,
Thank you for your clarification.
After trying many times , there are no other partition show up on Win8.1 for me.
But it works fine on Win10 and already start mining on my testing rig.
Thank you.
Good to know there is a problem with Windows 8.1. I only tested Windows 10.
Sometimes on any OS after imaging (with any image) , mounting will not occur correctly. It is always a good idea to disconnect and reattach a USB if it fails to mount after imaging.
Also, a USB key can sometimes become too hot after imaging and will not work correctly while hot, but will work normally after it has cooled down. Some USB keys models are more likely than others to have this problem.