The classic "Unable to locate WordPress Content directory (wp-content)" error

Hello.

I’ve been using WP for…2 days. Everything went fine under Windows. But when I tried to isntall the same zipped WordPress, I encountered this error. I am running Mandriva Linux 10.0, Xampp 1.7.7 for Linux, and the ftp program is PROFTPd. I fixed it but would like somebody to explain what I just did and WHY this hapened in the first place.

I fixed the linux problem thanks to this post:

http://wordpress.org/support/topic/unable-to-locate-wordpress-content-directory-wp-content-11?replies=21

I used this code to fix the problem:

define('FS_METHOD', 'ftpsockets');
define('FTP_BASE', '/opt/htdocs/wordpress');

Also, why does WordPress ask for ftp connection data everytime I have to update/install something. I know it’s because it ftp-uploads files into my local server, but why does this happen only under the Linux server?

Thanks