If you're unfamiliar with hard links, junctions, volume mount points, or Vista's symbolic links, skip the rest of this review--Link Shell Extension (free/donationware) is not for you. The advanced file system object representations I just mentioned weren't fully implemented in the Windows interface--most likely because they can cause confusion with the safer soft links, a.k.a Windows Shortcuts, that Microsoft did implement. Yet, they exist as part of the NTFS file system, can be useful under some circumstances, and these NTFS calls are used by LSE.
If you're unfamiliar yet still reading... As you probably know, a file name is a pointer to data stored in a file system. A file name/entry is also a hard link. That is, if the file is copied, moved or deleted, the same happens to the data itself. Changes to the file name don't affect the data. (Actually the data attached to a file name that's deleted will remain recoverable until overwritten, but that's another story.) LSE allows you to add additional hard links which function just like separate but equal alternate file names. As long as one is in existence, the data remains intact, that is, the space it occupies is reserved by the file system. Volume mount points are hard links that point to partitions. Junctions are hard links to directories. These are rather simplistic descriptions; if this is the first you've heard of them, study up before you use any of them.
Before installing Link Shell Extension, you must install the Visual C++ 2005 redistributable, which is available from the developer's Web site. LSE then installs itself as an integral part of Windows Explorer. To use it you select a file, folder or volume, right-click and select Pick Link Source, browse to the location you want add the link to, right-click and select Drop As, then the type of link you want. I highly recommend installing LSE into a virtual machine and playing with it there until you understand it as there is a potential for inadvertently losing data.
Link Shell Extension adds advanced object representations to Windows Explorer and is a powerful tool in the right hands. Most users can probably make do with Windows shortcuts. LSE is donationware so if you find it useful, please help the author out.