Task Manager > Performance Tab > Then press the resource manager button. Click on the qvs process, and then go to the Network Tab. Here you can see the ip address of the user who's consuming the most bandwidth through the TCP Connections (which is probably the most CPU as well).
Now open a command line and enter the following: WMIC /Node:IPADDRESS ComputerSystem Get UserName
so for example, my command is wmic /node:192.168.555.555 computersystem get username
Now I've got their username.
It's not exactly the best process in the world, but it works for me. If anybody has a better way of doing it, let me know.