LoL
Because it is probably a "community" family computer where lil sister has 1,000,000,000,000,000 songs downloading on her passworded account and the dude probably wants to play a online game, download some of his own music or even surf the net reasonably but he cant cause all the bandwith is eaten up.
Am I right ? If that is the case just try restarting the computer before you go on, that will shut down all of the other persons downloads. Or try asking them to halt their downloads until you are done with your time on the computer. It isnt too nice of them to still be using the computer even when you are on it. Its called compromise. If they dont go for that, then just restart the machine as I had said earlier.
Other than that I am not too sure what you could do software wise about it on the same computer.