All windows based PCs can be set up to follow QoS rules. QoS is Quality of Service, basically you can cap the bandwidth to each computer if you want, it can be enabled through the router.
If you want feel free to give me a PM, or email me @
andrewjurban@gmail.com
I'm graduating from University dealing with this kind of stuff all day long. The more I know about your setup, internet connection, etc The easier it will be to diagnose.
To rule some things out, its highly unlikely that your router isn't capable of pushing bandwidth to your desktop PC (if its connected through Cat5e(basic Ethernet cable) Generally routers appropriate more bandwidth to wired ports than wireless by default. However when you have two PCs fighting for speed, if no countermeasures are in place, its first come first serve on bandwidth.
But like I said feel free to PM/e-mail, we will get you sorted out!