Does anyone know how i can make a .com program (created to run on msxdos 1) run on msxdos2?

Basically every .COM file made for MSX-DOS 1 runs in MSX-DOS 2 as well. You can't have the program access files from a FAT16 partition or CD-ROM. For that you need to adapt the file access routines to use file handles as well. It also means you can use pathnames as well.

First you need to do a DOS version test (BDOS call $6F). If you save one of the results and read it later to open or read the file using FCB (DOS1) or file handle (DOS2). The file handle BDOS calls start somewhere from $40.

Info on all this you can find on the MSX Assembly Page.

Uhm...

i've made a simple Hitech c program that simply open a file on the floppy, save the content of a scr5 page then reload it from floppy.
actually i'm' using fopen,fclose fread fwrite (...old style..., not handle based).
this works fine in msxdos1 and on a floppy disk.

When i use an IDE interface (openMSX emulation of sunrise ide), the computer start fine, using msxdos 2. attemting to run the same program result in "*** Wrong msx-dos version" message-. It really does not load, neither starts !.

Why? What i can do?

try typing "set expert on" on the commandline.

Or better: download this tool... The set expert on trick will not anable you to neat stuff like UNDEL after DEL.

Thanks, i will test when possibile!