I've heard that the C: drive is usually protected because it contains the system files, but what happens if I take that drive and plug it into another computer? Can I format it there, or will I encounter some sort of warning that prevents me from doing so?
4 Answers
Yep, moving the drive to another PC means it’s just another normal disk. You can format it without seeing any warnings since the system protection doesn't apply anymore once it's not the boot drive.
You can definitely format the C: drive once it's connected to another PC. The protection only applies when you’re booted from that drive. When it's not the active boot drive, you can erase it without any issues.
If you boot the second PC from something like a USB drive, you can easily reformat the C: drive installed in that machine. There's no need to physically remove the drive; it just shouldn't be the drive you’re currently booting from.
Are we referring to an HDD or an SSD?

Makes no difference, the formatting process is the same.