Also try with the RewriteBase - uncommended. Now its commended.

The 500 has nothing to do extension with installation. It is clearly web server issues.
You should also try to backup your current .htaccess (as e.g. old.htaccess) and then to rename the htaccess.txt that is distributed with Joomla to .htaccess to see what happends. (possibly commentout the Option +FollowSymLinks there).

If the error still remains, then some further investigation will be needed.