There is an old utility called Casscopy for the Atari 8-bit that does a great job of copying self booting tapes to self booting disks. Be warned, it doesn't work on multi-load cassettes. These are tapes that load a title screen first, the tape pauses for a second and starts up again. This was done on purposely to keep from copying them to disk.
The Closer to Home web page probably has it in their FTP download area somewhere.
http://cth.tzo.com/index2.html
RE: emulators´ files to real disks