This function function establishes an NTFS hard link between an existing file/directory and a new file/directory. An NTFS hard link is similar to a POSIX hard link.
nt::HardLink "existing file","new filename"
Any directory entry for a file, is a hard link to the associated file. Additional hard links, created with the HardLink function, allow you to have multiple directory entries for a file, that is, multiple hard links to the same file. These may be different names in the same directory, or they may be the same (or different) names in different directories. However, all hard links to a file must be on the same volume.
Because hard links are just directory entries for a file, whenever an application modifies a file through any hard link, all applications using any other hard link to the file see the changes. Also, all of the directory entries are updated if the file changes. For example, if the file's size changes, all of the hard links to the file will show the new size.
When creating hard link to a directory the situation is a bit different. In these cases the original directory entry and the created links are not equivalent. If you delete the link then the original directory and its content remains untouched. However if you delete the directory any link to that directory becomes unusable.