First thought would be virus/malware on that system, or maybe some program eating resources that it shouldnt be. Might be worth using the tbb bandwith meter on these forums to monitor usage on the PC
I remember last year when i turned my Xbox One on it would slow my connection down. Turned out the xbox for some unknown reason was uploading a large amount of data. Factory reset of the machine fixed it.
Edited by bobble_bob (Wed 15-Jul-15 13:45:25)