Zend certified PHP/Magento developer

2 laptops slow internet to 0.07 mbps

We have 2 laptops in my house, CenturyLink, 15 mbps plan. When either one is connected to the internet, it’s blazingly fast and we get more than what we are paying for. If I connect the other one, it almost immediately slows to 0.06 – 0.10 mbps. Wireless or direct Ethernet connect, doesn’t matter. Which laptop doesn’t matter. Replaced the CenturyLink modem, same problem. Nobody I’ve spoken to has ever heard of such a thing. Any ideas?