Hey Elyptic,
You can choose a location for a new project at creation by clicking Down Arrow button on right side of Project Browser. It’s right above Create Project button. That will let you create a new project on your secondary drive.
Launcher automatically downloads example projects to C: drive. It’s a known issue and we are working to fix it. In meantime, you should be able to move those files from your C: drive to a secondary drive without any problems. If they were not fully downloaded because your C: drive was full, there may be problems with files, unfortunately, and you might need to make some room on your C: and try downloading them again.
Hope that helps!