Your right, fancy that OSX actually warns you that it's going to replace the file or folder, before it does it. "An item named "Runtime" already exists in this location. Do you want to replace it with the one you are moving?" In fact you have to click on the button that says "replace". I guess we missed that. dittoGUI is an OSX window to the Apple's Unix command ditto. Ditto leaves the folder structure in place and any files with unique names. It adds any Folders and Files which don't exist in the destination, and overwrites files which do. Ideal for merging in Runtimes. The best thing to do is to set up some test folders and files and experiment, before you work on your live data. I'm 80% through moving my Poser stuff onto another computer and have been using dittoGUI a lot. I think it's call "eating your own dog food"