I can't help you with the network issue, that's probably an issue with the Dell laptop that maybe doesn't support WPA. You could try disabling it on both the iMac and the router and see if you can get the laptop to work that way, but then you'd be without security. You could try WEP, but that isn't very good. Maybe get a new wireless card for the laptop.
For the other parts, you can download freeware at places like MacUpdate to remove that stuff. I use Delocalizer and Monolingual to remove language files. I think you can manually remove printer drivers, but it doesn't take up that much space.