Limit bandwith for clients on LAN?

You need an actual router with QoS firmware (like a Linksys), or you need to set up one computer (not one of the two you're using now) as a router - Freesco can bandwidth limit (or do almost anything else that a router can do). 'Freesco' stands for Free Cisco. It's a free router that can run from a floppy disk (but it needs some kind of computer, with at least two ethernet cards - it can be a very old, very slow piece of junk).