HTML Help Workshop must be installed to c:\program files\html help workshop - surely not!

Upon installing a NAnt script to our development server I began experiencing the following error - during the documentation task which uses NDoc to generate XML and CHM help files - MSDN style (using the MSDN documentor in the NDoc task).

Unable to find the HTML Help Compiler. Please verify that the HTML Help
Workshop has been installed.
Unable to find the HTML Help Compiler. Please verify that the HTML
HelpWorkshop has been installed

Of course, I had never had this problem on my own development machine - a machine running pretty standard installations of Visual Studio 2003 and Visual Studio 2005.

Naturally, these tools were not on the server.

So, initially, the HTML Help Workshop was not installed on that server. After downloading a setup for it from Microsoft I installed it onto the D: of that server - I like to keep unnecessary tools etc of the system drive (C:). However the error remained.

After trolling around for quite awhile not finding much, I had picked up a couple of clues as to where NDoc seems to get the information regarding the location of some of these external files (such as the help compiler hcc.exe) (see the XML configuration files under NDoc\bin\net\2.0). Anyway, it appears that the Help Compiler needed to be installed on c: drive.

Sure enough after removing my initial installation and re-installing it, this time to c:\program files, the NDoc task in the NAnt script worked!

I can't believe this is the final answer! Surely not. Surely there is a config file setting somewhere - of a registry key for the HTML Help Workshop I can set to avoid this???