In that case I'm afraid we're not sure what's going on there. There weren't any reported issues with the installed files themselves causing bugs or issues, so it should be fully safe to install it to your C drive. However, we understand that you may be reluctant to do so from an Indie developer, and would ask you to please email us at:
gamespeppermint@gmail.com
so we can create a new installer for you, or send you the zip file directly, whichever is your preference