I don't have a lot of space on my C: drive so I can't install Hitfilm on there, but when it pops up to make me change the drive, no matter how much I click on my other drives, it won't let me change it to that drive.
Are you doing a "Custom" installation? That's the only way to set a custom drive path.
Bear in mind, if you're a Windows user, even if you install Hitfilm to the drive, a lot of files end up on C:, anyways. There are files Windows needs and expects to be on C:
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