Limit Bandwidth to a particular IP Address.

I would like to know if there is a way , via software to restrict traffic to a particular IP address on my lan .

I am connected in the following way .

ADSL Modem -> Switch -> Desktop / Laptop

I have set static IP's for both machines

Desktop = 192.168.1.6
Laptop = 192.168.1.2
Default Gateway = 192.168.1.1

I have a 256 Kbps unltd connection from Airtel .

Is there a way to split the traffic 50/50 128kbps for the desktop , 128 Kbps for the laptop ? cause the moment my brother starts downloading the switch dedicates all of the 256 Kbps to his machine , my browsing begins to crawl then