Python install doesn't include VC++ redistributable
If you install the Mercurial package from scm-manager (using the "start configuration wizard" (used the "f1ea71" package). It doesn't include a Microsoft Visual C runtime DLL that is needed for python to run. You get an error of "The system cannot execute the specified program." if you try to run the python.exe on the command line.
I saw this on a clean install of Windows Server 2003 R2.