Question : Internet slows Down

On our network when the PC's come online, the internet slows down! I think one of them is sucking up bandwith.
is there a free tol I can download to check what is causing this?

Answer : Internet slows Down

Etherscout demo http://www.majorgeeks.com/EtherScout_d4088.html does a pretty good job, but limited to 10 pcs only, don't know how many you have on your network.

Klir Analytics also has a good product  http://www.klir.com/products/bandwidth.html?gclid=CNGSr6m1i4oCFRBoNAodsGimRA  this one limited to 25 pcs on demo version.