Couldn't trash folders


Clean iBook, formatted with one partition HFS+. Installed OS 9, installed OS X. Everything works fine. Then I booted up in OS 9 mode and upgraded to 9.0.4 wich put two new folders on my desktop; "Tools" and "Programs & Accesories" (is that the correct name? I'm not running english OS 9 so I'm not sure). Anyway, I rebooted in OS X mode, put the contents of these folders in the corresponding folders in the MacOS 9 folder.
Then I tried to put these two empty (?) folders in the trash but I wasn't allowed to. "You are not allowed to throw away..." was the message. Tried from command line and found that the folders weren't empty, the contained a file named ".DS_ something", wich I couldn't delete either. So I "su'ed" myself to root and then it worked. What is this? If
OS X is supposed to be any mans OS, things like this shouldn't happen. Could someone explain?