When a program is RUN from BASIC, the following occurs:

1. The file is opened with firmware function "CAS IN OPEN",
2. The data is read with firmware function "CAS IN DIRECT",
3. The file is closed with firmware function "CAS IN CLOSE".
4. Then the program is executed using firmare function "MC BOOT PROGAM" with the execution address taken from the file header.

Therefore, for a file to be RUN it must have a file header.

The disc operating system and roms must be re-enabled