>>Probably different IIS/OS versions (I'm looking at a W2003 server). If the option is not available from your IIS context menu, can't you use the Windows Explorer to set permissions?
>
>Nope, I just get the web sharing option. I'm using IIS 5.1 on XP Pro

Assuming you have administrative rights on your current login, you may turn on the security tab in Windows Explorer through (I'm not exactly sure of this, but at least it may serve as a rough guide) Tools : Folder Options : View : Advanced : and... er... something to do with file sharing... (sorry... I have a XP box at home, can check it later).