I updated the quote box in my posting #7 above. All this can be done in the same way also with integration with Photopost Pro and Classifieds. Here is the description:
1. upgrade Reviewpost if not using the latest
2. & 3. install phpbb3 & convert at the same time old vb3 forum
(use "vb3 converter" of the phpbb3 site to import old vb3 forum into new phpbb3 -> step 2 & step 3 have to be done simultaniously)
4. empty the pp_usergroups table in your photopost database (with phpmyadmin) so on next step your phpbb3 usergroups will get imported
5. Upload again the file "install.php" on your server. Rerun photopost install like a fresh install using same prefix and databasename of the old Reviewpost installation. With this step you integrate now with phpbb3. This will not delete data. There will be errors because it can not overwrite the data, ignore them. It will only write data in the empty pp_usergroups table of step #4.
6. Upload the userfix script from here on your server in the RP root directory and run it through your browser. This script makes sure, that all users have really the proper User-ID
7. Compare your Cookie prefix names in RP and in phpbb3. Change it so that they are the same, otherwise global login does not work.