The obvious way to prove the culprit (and I would suspect the adapter, given that the wireless link still gets its internet connection promptly) is to swap your Ethernet cable into the port on your laptop. No config required to speak of, other than the usual firewall permissions. Turn the firewall off for convenience while you test it. If work as normal, then the desktop adapter is to blame. If it's just as bad, then try a different RJ45 port on the router. If that's still duff, then the router is up for replacement.