Is it possible that you have a seperate external volume control dial on the speakers/headphones? If so, then check that to make sure it is disalled up.
Regards,
Golden
My Computer
At a glance
Windows 10 Pro x64 ; Xubuntu x64Intel i7 860 @ 2.80 GHz O/C'ed to 4.0GHz16GB Corsair Vengance DDR3 @ 661 MHz Dual Cha...EVGA NVidia GTX 560 1024MB
1*Samsung 840 EVO 120GB SSD;
1*OCZ Vertex 2 60GB SSD;
2*Samsung F3 SpinPoint 1TB in RAID0;
1*Samsung F1 SpinPoint 1TB;
2*Western Digital 1TB External USB 3.0
1*Western Digital 500GB External USB 3.0
1*Seagate 500GB External USB 2.0
PSU
Thermaltake ToughPower QFan 750W
Case
Thermaltake Element S VK60001W2Z
Cooling
Corsair H60 Water Cooling, 2*230mm and 2*80mm case fans
Now a basic question. What are you playing? Are you sure that the source itself is not at an abysmally low level?
The other thing you can try is:
Open the "Communications" tab in Sound dialog box and then select "Do nothing". Cick Apply, OK and close the dialog box. You may need to restart the PC for the change to take effect.
Check whether this returns the volume to normal levels.
A bug in Windows 7 is supposed to reduce the volume, even when no communications is on in some cases. (Not all)