Limit p2p bandwidth/traffic?

well, i have a brother and he uses Frostwire(p2p software) a lot. whenever he uses it my download speeds suck. browsing web pages is really slow as well. the average speed i get when he is using frostwire is around 11kbps. now i went into the options and change the download speed from unlimited to something else lower. he noticed the download speed was slow and he changed it back. he is not completely computer illiterate but he knows where to look around. we are both using WLAN connections and connecting to a linksys wrt54g router. is their anyway i can limit the amount of bandwidth he uses for frostwire or the amount of bandwidth for his whole computer without having to buy software? i will do anything to be able to use my web browser on a regular basis. ALL help is very appreciated. thank you :D