We package the Python.org installer inside the Slate Desktop installer. Our installer runs the Python installer using a command line values that adds Python to the the system %PATH%. Some users report this fatal error during the installation. This error results from a bug in Windows msiexec system.
There's an easy work around. Download the Python installer from this link:
Then run the installer. During it's installation, it will prompt you for several options. Select the option to add Python to the system path. Once Python is installed, run our installer again. Our installaller will find Python and skips running it's own Python installer.