Issue Installing Mounting .iso Images in Windows 8

Hi-I have VM Fusion 5.0 on an iMac, I've installed a Windows 8 64 bit machine that is working fine. I try to install an Microsoft Office 2013 64 bit drive from an .ISO image, though, and it won't mount - either with the native functionality of Windows 8 or with Virtual Clone Drive.

Any thoughts?

Thanks

Vern