We are currently adding Hyper CLI path to user PATH in Windows registry: https://github.com/zeit/hyper/blob/262eb8ad9b7b9b15351f331765151538d67a09e2/app/utils/cli-install.js#L49-L91

A caveat is that environment variables are cached and users should open and validate "Edit environment variables for your account" dialog to force a cache refresh (or simply reboot their workstation).

@Stanzilla gave a link that could help to improve this: https://stackoverflow.com/a/11955920