Internet speed

Hello,
in my room we have internet accss for 5 laptops using wireless router.we can find easy to browse and watch movies easily . when one of my friend runs his system the internet gets down and making some time to buffer and play. when he switched off it is back to normal process.but that guy can run internet esaily when we r struggling. so give me some solutions . and i need to make my system more than others . describe me how to do

thanks