This is a converter script, which creates C64 Magic Desk cartridge files in CRT format from PRG files. It is tested with Python 2.7. First download the script and then call it like this:
python.exe prg2crt.py test.prg test.crt
In Windows the Python interpreter might be not in the path:
c:\Python27\python.exe prg2crt.py test.prg test.crt
It uses some inline assembler, which copies some code to the screen buffer, which in turn copies the PRG file content from the cartridge ROM to RAM and then calls the BASIC "RUN" command. This is the loader source code: loader.asm
Example output from this project (final step 100): test.crt. Tested in VICE.