that sounds rather weird. so you're saying that if you don't turn on your gaming rig, internet connection on your laptop is fine?
and both are connected with ethernet cables to the same switch/router?
assuming that all the wiring and basic networking is correct:
sounds to me like something on your gaming rig could be demanding too much of your internet connection (thinking about a trojan horse or something) to check that, use a windows command shell and type (on your gaming rig) and type "netstat -an". it will show you your active connections using tcp and udp protocol.
the result looks something like that:
Active Connections
Proto Local Address Foreign Address State
TCP 0.0.0.0:135 0.0.0.0:0 LISTENING
TCP 0.0.0.0:445 0.0.0.0:0 LISTENING
TCP 0.0.0.0:5357 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49152 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49153 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49154 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49155 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49156 0.0.0.0:0 LISTENING
TCP 0.0.0.0:50000 0.0.0.0:0 LISTENING
TCP 0.0.0.0:51502 0.0.0.0:0 LISTENING
TCP 127.0.0.1:2559 0.0.0.0:0 LISTENING
TCP 127.0.0.1:12025 0.0.0.0:0 LISTENING
TCP 127.0.0.1:12080 0.0.0.0:0 LISTENING
TCP 127.0.0.1:12110 0.0.0.0:0 LISTENING
......
not using any application that obviously connects to the internet, how many of those entrys do you see that have a foreign address (means NOT 0.0.0.0:0 or 127.0.0.1:xy) and say in state "established" or "listening"?. Do you also use your network for filesharing between your computers? if yes, how's that coming?
i am absoultely sure that i just raised more questions than i answered, but i feel we're getting somewhere with this
thanks for your patience and tolerance anyway 
Edit: By the way, did you check your bandwidth ? what is your rated download speed and what's the real thing right now (tip: start to download something from http://mirror.switch.ch - very well connected public ftp server (linux images and stuff), directly attached to switzerland's primary internet backbone).
and both are connected with ethernet cables to the same switch/router?
assuming that all the wiring and basic networking is correct:
sounds to me like something on your gaming rig could be demanding too much of your internet connection (thinking about a trojan horse or something) to check that, use a windows command shell and type (on your gaming rig) and type "netstat -an". it will show you your active connections using tcp and udp protocol.
the result looks something like that:
Active Connections
Proto Local Address Foreign Address State
TCP 0.0.0.0:135 0.0.0.0:0 LISTENING
TCP 0.0.0.0:445 0.0.0.0:0 LISTENING
TCP 0.0.0.0:5357 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49152 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49153 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49154 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49155 0.0.0.0:0 LISTENING
TCP 0.0.0.0:49156 0.0.0.0:0 LISTENING
TCP 0.0.0.0:50000 0.0.0.0:0 LISTENING
TCP 0.0.0.0:51502 0.0.0.0:0 LISTENING
TCP 127.0.0.1:2559 0.0.0.0:0 LISTENING
TCP 127.0.0.1:12025 0.0.0.0:0 LISTENING
TCP 127.0.0.1:12080 0.0.0.0:0 LISTENING
TCP 127.0.0.1:12110 0.0.0.0:0 LISTENING
......
not using any application that obviously connects to the internet, how many of those entrys do you see that have a foreign address (means NOT 0.0.0.0:0 or 127.0.0.1:xy) and say in state "established" or "listening"?. Do you also use your network for filesharing between your computers? if yes, how's that coming?
i am absoultely sure that i just raised more questions than i answered, but i feel we're getting somewhere with this


Edit: By the way, did you check your bandwidth ? what is your rated download speed and what's the real thing right now (tip: start to download something from http://mirror.switch.ch - very well connected public ftp server (linux images and stuff), directly attached to switzerland's primary internet backbone).