Slow download speed

I have 2 laptops, one via ethernet gets 870 Mbp/s download via speedtest while the other fluctuates between 150/450 Mbp/s. To make sure it wasnt a placebo effect I brought the malfunctioning laptop to the exact same ethernet cable and did a speedtest, as expected the working laptop got 870...

Basically, my PC is getting anywhere from 0.4mbps-10mbps when other devices are getting 55-60mbps. I just bought a new wireless USB adapter thinking mine had quit on me but it's not helping either. Basic specs are as follows: AMD FX(tm)-8320 8 core 3.5GHz 8gb ram windows 8.1 64-bit NVIDIA...