Assuming Windows, NTFS has a hard link feature, but it's not generally accessible via the OS. Good show. I think there are utilities out there that'll let you create them, but I don't know what the impact might be.

If he's using an OS without NTFS support, like 9x or Me then he's out of luck.

Googling on "ntfs hard link" turned up some stuff, including utilities to make them. There was also a reference to a MS KB article on how to create them that's since been deleted.