Files merge when I replace a folder?

When I drag and drop a folder to replace a folder with the same name, instead of replacing the contents it leaves behind files it should have deleted in the replace action.Setup a test as if you have two folders with the same name and same contents on two different drives (you can actually do the test on one drive). One folder is your backup and one is your working folder. You decide to cleanup the working folder and delete one or more files. Then you decide to replace the backup folder. When you copy the primary folder to the parent of the backup folder, you are asked if you want to replace the folder. When you answer Yes, the folder is copied to the destination, but the files you deleted from the primary folder are still there in the backup folder. Now I can see how this would be a benefit to those who often make mistakes when doing backups and file management like this but for me this feature is annoying. It means I have to first delete the backup folder before making a backup.Here is another way to explaining this:C:\Working\Photos\Image1.jpg, image2.jpg D:\Backup\Photos\Image1.jpg, image2.jpgDelete Image2.jpg from folder C:\Working\PhotosDrag and drop C:\Working\Photos to D:\BackupPrompted to replace folder D:\Backup\PhotosContents of D:\Backup\Photos still contains image2.jpgInstead of replacing D:\Backup\Photos it merged the files. I would really like to know what MS calls this feature and how to turn it off.Bob