To access an external hard disk drive that was attached to a Windows machine that was not properly shut down, and you cannot mount it in Windows, plug it into a Linux box. There are useful NTFS utilities on GNU/Linux that can fix this issue. I used this on Gentoo.
ntfsfix -d /dev/sdb1
This fixed the issue with the external hard disk drive and it was read straight away on Windows. I could not even see it at all in Windows with Disk Management as Administrator. Very strange behavior. A user should expect Windows to be able to see all hardware, but no. I could see all Linux partitions that are EXT4, but not a bugged NTFS partition? But this is how I fixed it anyway. The ntfsfix utility should be a part of the ntfs-3g package, and any modern system would already have this installed.
More information about the ntfsfix command on Linux.