>When I try to install R2, it tells me that the version is not compatible or something like that with the current version I have. So, it is probably something between Standard VS Developer. How would I know which version is currently installed? When we go in Add/Remove Programs, the edition is not listed.

See http://www.berezniker.com/content/pages/sql/microsoft-sql-server/retrieving-sql-server-edition-version-and-service-pack-info