Using Windows own tools., I'm out of options then. You might have to use the 3rd party tool that Mark already mentioned, or if you have a Linux distro live disk laying around, use Gparted(or down load it here). Get the ISO and either burn it to a USB or DVD and then boot into it. I usually use this. Here's a couple of screenshots of it from my VM, note what the dropdown menus offer:
What drive are you trying to use? I have a USB 3 iomega eGo that with Windows 10 completely fails to work. Windows 10 will read from it but not write anything larger than a few KB and can't format it. If I try any big writes explorer hangs and I have to shut down.
In my case it is the Microsoft UAS driver (version 10240) that is the problem. The Intel one in Windows 7 still works as does Linux and OSX on the same hardware.
Windows 10 will happily use it through USB 2 but not USB 3 UAS. According to iomega website my drive isn't compatible with windows 8 so this might be your problem also.
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