Check for viruses and ad/spyware. That should always be the first thing you do.
Does the router have a firewall? Is it set up, and set up correctly? Is the computer running a firewall?
Open up the Device Manager. Control Panel-->System-->Hardware-->Device Manager. Look for anything with a problem...it will have a yallow exclamation point, or a question mark. If you see one, doubl-click the device and see what it says is the problem.
My Rig: SABLE
Antec 300 Illusion / Antec EarthWatts EA650 650W / EVGA GTX 760 2GB
AMD FX 8320 x8 Black Edition / Gelid Tranquillo / MSI 970A-G43
Sandisk Ultra Plus 128GB / Samsung 840 120GB / WD Black 750GB / WD Green 1TB / WD Red 3TB
G.SKILL Ripjaws 2x2GB DDR3 1600 - Crucial Ballistix Tracer 2x2GB DDR3 1600
Win7 Ult 64-bit - Func MS3 Mouse - CM Storm QuickFire Rapid Mech Keyboard
R.I.P. Danny L. Trotter
... 14 Nov 1945 - 4 Sept 2009