You might check this. Right click the speaker icon and select Playback Devices. You should show at least speakers and headphone. Select each in turn and click the properties button then the Level tab. Try setting levels on each device there and see if it helps. You may have to right click in the Playback Devices windows and select show disconnected devices.
If you do not show both devices, perhaps you need to right click the speaker icon and select Volume Control Options and check all devices currently playing sound.
If that won't help, I would have to agree with kemical about a special utility might have done what you want in the past. Perhaps it works differently in x64, or you haven't loaded the x64 version of some driver.