Thanks Helen.
The first solution didn't work for me, althoug I think I didn't use any new feature. Finally I used the second option.

--- In firebird-support@yahoogroups.com, Helen Borrie <helebor@...> wrote:
>
> At 08:30 PM 21/12/2009, you wrote:
> >Does anyone know how to convert a database version 2 to old version 1.5?
> >I tried to backup in Firebird 2 and then restore in Firebird 1.5, but I got the error message Expected backup version 1, 2 or 3. Found 7.
>
> Something you could try (with no guarantee of success) is:
>
> 1. Rename gbak.exe in your Fb 2 installation.
> 2. Copy gbak.exe from the Fb 1.5 kit into the /bin directory of your Fb 2 installation.
> 3. Use this executable to back up the database, under the Fb 2 server.
> 4. Try to restore this backup under the Fb 1.5 server.
>
> Note, it can't work if you have used new features to alter objects. This includes the rebuilding of character-set-sensitive metadata.
>
> Otherwise, pumping the data back into a scripted empty database or a metadata-only backup taken from a restored copy of the original database is the way to do it.
>
> ./heLen
>