thank you for your kind reply.
I did know the Bitnami Links that you provided me. The "How to upgrade Alfresco" I will try it as soon as possible. And I reall hope the upgrade will go well.
As for the backup link you sent, we used it but my collegue that was trying to import the database, got the problems described on my first post.
I then got success importing data from the Share, exporting from Alfresco 4 acp file and importing it with a rule in alfresco 5, but, unfortunatelly, it didn't import the rules, the categories and the tags. Damn!
So I will try with my collegue, that knows linux and programming languages way more than I, to upgrade the Alfresco 4 bitnami machine.
If we will have problems, I'll write again. By now, thanks for your help, it was much appreciated.