There are not a lot of free bandwidth limiters for Windows as they normally require a driver to be installed, and it costs money to have them digitally signed. I used the free edition of Net Balancer in the past and it did the job.
But I would see if your router has any QOS ( Quality of Service ) features as it applies to all devices and is far more effective in a shared household, especially with bit torrent traffic.
If your router does not have built in QOS features, see if it is compatible with something like DD-WRT which provides more options.