Windows 8 will be able to mount ISO and VHD files without the need to install third party software such as Daemon Tools or PowerISO. To mount an ISO file, right-click on the file for the mount options or select mount from the enhanced Explorer ribbon. Double-clicking on the file will also do the trick.
For a VHD file, which is a Microsoft proprietary file format for a virtual machine's hard disk, mounting it will make it appear as a hard drive on the Windows 8 system.
For more information on these exciting new features of Windows 8, please follow this link.