Ah, I see. That's annoying. Surely someone could just look at their registry and give you the installation directory entry?
Here's what mine says. I suppose if you add the bits I've highlighted in red, the .exe should find your installation? PLEASE DON'T TRY THIS UNLESS YOU KNOW WHAT YOU'RE DOING!
Edit: ****! I've just noticed that they're pointing to my CD drive, not my HD (so many drive letters!), and so this won't be any of use at all! I'm sure there's an installation dir entry somewhere. There must be! Sorry!