I've not really played around with windows networking much, but I've just ended up with 2 comps & so am looking at file & printer sharing. File sharing is all fine, but there's one thing which surprised me when sorting out printer sharing. If I browse comp 2 from comp 1, I can see all the printers installed on comp 2 - this is irrespective of whether they are explicitly shared or not. I can also print to them and alter their settings with no problems. So what exactly is the point of selecting the 'share this printer' radio button?
Both comps are running XP Pro, and I'm logging in as myself (admin) across the network (Guest user is disabled).

