I am connected to comcast with a SB5120 into my desktop running XP. Testmy.Net shows that I am running at T1 speed versus 6Mbps. Connecting through USB or NET makes no difference. Testing under Internet Explorer vs Modzilla makes no difference. Comcast came to my house. Using a notebook running XP and my network (cable, modem, ISP) they approached 6.0Mbps. They said that "something" in my desktop is the problem. I'm a newbee and don't know where to start. Any suggestions on isolating the problem?