There are a few ways to clean up filenames to make them legal for transfer; I've used both FileBuddy and A Better Finder Rename with success, and ABFR even has an "NTFS legal" preset for quick action. For a single-purpose tool, though, there's now NTFSready, This 10-euro donationware tool will hunt through your files and folders for illegal characters, nuke them, and that's about all there is. Is it worth it? Well, if you need to rename files for NTFS use on an everyday basis, maybe. At 10 euro, though, I'd say you're better off paying the $19.95 for ABFR and getting the flexibility that comes with it.