Check out
http://www.spellquizzer.com/MicrophoneBoost.htm
(Or google mic boost for your operative system for further tutorials.)
There is explained how to turn on the feature Mic Boost if your sound card allows it.
Mic boost helps lowering the static noise coming from the hardware (not the background).
(This is actually very helpful anyway. You may want to check if your issue is already fixed.)
Now, your problem comes from the background so what you do is to lower the volume of your microphone (there is a slider for mic volume in the settings you just checked there).
Finally sing or speak with some "hit" to the mic so the ratio voice/noise is high.
Lowering the mic volume will lower faint sounds while with mic boost you still have good sound power.
If the problem still appears it's because your ratio voice/noise is too unfavourable. You need to get stronger voice or lower noise.
If you can't use a stronger voice (because you want to record a weak voice, for example) you will need to lower the background noise.
And one of the easiest ways is to just isolate yourself from the noise source somehow.
One of the cheapest ways is to just get a blanket or a towel and put it over your head and your microphone so the noise "keeps out" a bit. (It also helps with echo that may cause problems with UTAU samples.)
Of course there is also the
super expensive option of getting some kind of isolation booth like a "room-in-a-room" soundproofing.