other than images and files uploaded by users, the content is stored in the database so if you really lost that you might as well start over.
If you don't have knowledge and experience with databases and if your site is likely to have limited traffic or for just experimental sites, you might be better off using our mojoPortal package for SQL CE (Sql Sever Compact Edition). SQL CE is not as robust as a real database platform like MS SQL but it can be much easier to work with because there is no separate database software to install and the database is just a file on disk that you can easily backup or move from one place to another. However, the mojoPortal Web Store feature is not included or supported with SQL CE, so if that feature is important to you then you should use MS SQL.