Dear George,
usually this message occurs when there's a mismatch between the python version(32/64bit) and the vmtk version (32/64bit).
The vmtk installer, which is based on python distutils, is not able to find a valid python installation in the windows registry.
Sometimes this message was due to python Anaconda installation which under windows does not copy itself in the registry.
If you are sure that:
- both python and vmtk installers are 64 bit
- python is 2.7 and not 3.x
- python is default python and not python anaconda
You should try to remove and reinstall python 2.7 64bit:
Best Regards,
Simone