Yeah, you lost the resource fork.
Mac files can have multiple forks making up a file. (Actually, so can Windows files on NTFS; they're called Streams.) However, Windows Explorer only reads the primary stream, or data fork. If you use Windows Explorer to copy a file, it will strip out all the resources/streams.
Mac fonts often consist entirely of resources outside the data fork.
You need to connect the disk to a real Macintosh to recover those fonts. If you want to save them on a PC, you can pack them into a Zip archive or disk image (DMG) on the Mac first.