Wireless internet unbelievably slow on one computer

My internet is so painfully slow on my desktop computer. It works perfectly fine on all the other laptops/tablets in the house, (roughly 6-10mbps) whilst my desktop only gets 0.4mbps (sometimes less). It is so slow I cannot even load a webpage - it makes the desktop unusable. It has not always been this slow. I have ran a malware bytes scan and nothing came up. I did a factory reset, and it changed nothing.
My specs are:
CPU: AMD FM2 A8 6600K APU Quad Core CPU 3.9Ghz (turbo 4.2Ghz)
Motherboard: Gigabyte F2A68HM-HD2
Memory: 16GB DDR3 1600mhz Memory
Graphics Card:ATI 8570D APU Graphics
Hard Drives: 1TB Seagate Sata 7200RPM 6Gb/s Hard Drive


Please tell me any information I need to include to fix this problem as it is driving me insane.

I have to deal with 2 wireless activities, one is the Wireless DSL that actually connects to the Internet through a dish with modem aimed at an antenna farm and the other is the Wireless/Wi-Fi Networking in my house. I have desktops connected through Ethernet cables to the Routers and Notebooks connecting through wireless to the Router. The Wired connections are Gigabit and most of the Wi-Fi are 802.11g/n, don't see many problems with them. The Router and a Switch are 10/100/1000 and the Wireless in the Router is 802.11n. If your desktop is wired to the unmentioned-Router it may be the Network adapter is having issues with the Router.