You can change drive letters. So you could copy, then swap the drive letters between partitions.

But for the OS it’s not so simple - at least for Windows. Specifically because of the Windows registry and hidden profile data and Windows activation.

By that point I’d consider a file copy, registry backup (for selective restore; but may not be worth it), and reinstall Windows on the new partition. Trying to clone-move in a working way is a hassle and error-prone. I’d consider ensuring getting the Windows license over much easier. (A documented workflow by Microsoft.)

Loss of registry means many things may have to be reinstalled and reactivated, but I’d still prefer that.