Are you a total Drupal beginner? Do you use a one-click installer like Fantastico or QuickInstall that came with your hosting account and need to reinstall into a directory that already has Drupal installed? Sometimes the /sites/ directory just won't allow itself to be deleted.
Don't worry, you're not the only person to have that difficulty. This an easy way to delete that directory so you can do a clean install with a one-click installer or just clean up your server. This is written for the absolute beginner. Don't worry, you don't need to download putty, get command line access or call anybody. Here's how to delete the /sites/ folder: