If your main page works fine but you get an error on any other page you like to visit, check the following things:

• .htaccess file should exists and should not be changed from originally downloaded archive
• mod_rewrite module should be enabled in Apache. If you can't see the string "mod_rewrite" on text generated by phpinfo() function that means that you need to enable this module
• AllowOverride and FollowSymLinks enabled in Apache configuration (if you configure server by your self)

One user has reported that this problem was fixed only by moving the website from subfolder to the root.

One user has reported that he has got error "500 Internal Server Error error". That was solved only by adding a slash to .htaccess file:
RewriteRule ^(.*)$ /index.php?%{QUERY_STRING} [L]