Unplug the cable that runs from the modem to the router and plug it into your computer so the router is no longer part of the setup. If you get a connection without a problem then it's not the NIC.
One thing you might want to do is click start>control panel>system>hardware>device manager>network adapters. Double click on the adapter and then click on the tab says power managment and uncheck the box that says "allow the computer to turn off this device to save power".

Also your post is kind of unclear, do both computers still connect to the internet?

99 Contour Sport SE MTX KKM filter, B&M shifter No res, BAT kit Green car silver hood (because silver is faster)