There's tons of threads on this forum about symbolic linking, most of them are about issues with symbolic linking and the way that vista manages administrator rights. The easiest way to get it to work (without having to resort to command line tools and scripts) is to install a shell extension that will do it for you:

http://schinagl.priv.at/nt/hardlinks...kshellext.html

The above application allows you to create symbolic links in almost the same way as you would normally copy a folder (by using your right mouse button menu). All you need to do now is:
- Create normal copies of your wow directories
- Delete the data and patches subdirectories (in the copied directories)
- Delete the wow executable (in the copied directories)
- 'Copy-paste' the data subdirectories as symlinks (or junctions, depending on your OS)
- 'Copy-paste' the wow exe as a hard link