Computer sound is very quiet on certain apps/games?

When in firefox youtube is very quiet and when i play certain games like mount and blade warband I have to turn the sound on all the way to atleast hear something. In chrome on youtube it does not do that. I cleaned my registry but still nothing. Im using headphones but that is not the problem because they work fine elsewhere.|||Under the youtube video look for a slider for sound. If its not that, click on the sound icon to the left of the time on your screen. It should come up and underneath it will say Mixer in blue text. Click that then open firefox. There will be a few volume sliders. Make sure firefox is put into the middle. if it already is, put it all the way up.