You could try changing the Channel number used by the Router to broadcast the WiFi signal. The default channel number for most routers is normally "6" or "11" so try one of those or, if already on one, try the other.
Make sure there are no large metal objects, such as radiators, in the line of sight between adapter (PC) and router. Also keep cordless/mobile phones away from adapter/router.
>>> it says i should have an excellent connection throughout my house
Yes, but are you also using a compatible 802.11n router to be able to benefit from the improved performance offered by the adapter?