To whom it may concern.
I've been reading the sql scripts from 2.0 version. I looked for all changes necessary to update from 1.3.3.
I made an script with all SQL sentences needed to update and runned it over 1.3.3 database and then run 2.4 version install.php. Now I can login and all seems to be correct, but I haven't do too many test.
If anyone wants to test it, ask me for a copy. I've tried to paste here but there are too many characters.