So I have to restore the db at first instance? then I logon into OpenErp on that db and I install addons?

the addons are already installed in the database, if they are the same addons you used before.

Thanks, i had to start a new db, install all modules, create user equals as an old db, and, then restoring old bd with another name. Then i erased new database and changed name to old db to new's db name.

Now i'm with other problems and i'm trying to solve them updating addons.

All problems solved. I followed the next steps:

New installation of OpenERP and Postgre, new db with the same parameters of backup db. Log in in OpenERP, installing all modules as in the backup, changed admin name and pass to backups parameters. On pgAdmin erase new db, and import backup, renaming this db to the erased db name. Log in of new at openerp, and upgrading modules who causes errors.