By default, a clean installation of Windows or macOS is designed to target the (usually your C: drive). It does not automatically reach out and "sanitize" your secondary D: drive, external backup disks, or secondary SSDs unless you manually intervene during the partition process. How a Clean Install Works
While the process is exclusive to the drive you select, human error is the biggest threat.
If you want to be 100% certain that your secondary drives remain untouched, follow the rule: