PyEnv is great, but it's not available on Windows. This article provides a workaround that does the following:

1. Installs each python version

2. Rename the python.exe file within each python directory. For example, python35.exe within the python 3.5 directory.

3. Add the python directories to the windows environment variable.

In your situation, it seems like the system can't find the python37.exe file, so I would make sure the python 3.7 directory is added to the windows environment variable.

Feel free to reach back out for further assistance. =]