Very important! When mounting an NTFS filesystem that is also used by Windows, always specify the windows_names option, both in /etc/fstab and when using mount.ntfs.

Windows is not fully compliant with the NTFS specs, which is a bloody genius move on Microsoft's part. NTFS allows file names and paths to contain characters that are illegal in Windows, like the : character. If you create a file with such a name, it will make the volume unmountable. Ask me how I know. The windows_names option prevents that.