In continuing to research a solution for this question on ServerFault:
https://serverfault.com/questions/221203/mercurial-hook-fails-on-windows
I discovered an interesting and somewhat disturbing thing: I have seem three different versions of Python on my machine (four if you count the "official" version which doesn't appear to have a DLL with it....). Here's shot from my file search tool:

More Info:
- I am running Windows 7 64-bit
- Both the TortoiseHG and the Mercurial directories are on my path, with the Mercurial directory listed first.
- I have Python 2.6 installed in c:\Python26
- I have no entry for any type of PYTHON-based environmental variable. (Should I?)
I suspect that this is the source of the my problem from the question above, but I thought I'd ask here, as this is particular issue is a Python deal.
I tried to replace both DLLs with each other, but when I use the one that comes with Mercurial, then TortoiseHg stops working.
It seems to me that "there should only be one" Python on my machine. How do I achieve that?