Windows 8 has the ability to natively mount ISO images. But how to know which ISO file is mounted in a virtual drive?
At the PowerShell prompt:
To find the drive letter corresponding to an ISO:
Get-DiskImage -ImagePath "full_path_to_image" | Get-Volume
To find the ISO corresponding to a drive letter:
Get-Volume -DriveLetter F | Get-DiskImage
"F" is obviously the drive letter. Also, you can try omitting "-DriveLetter" to shorten the command. If you omit both "-DriveLetter" and the letter itself, you should see info for all volumes.