Razer made these headphones "Plug and Play". They are NOT part of your Realtek Soundcard, instead they use a generic Audio Driver.
My suggestion. Disable your soundcard in BIOS, so that your computer will recognise Razer Megalodon only. To check, Right-click My computer>Properties>Hardware>Device Manager>Sound, video and game >LOOK FOR USB AUDIO DEVICE
Also, make sure that your stimulated speakers all have volume by pressing the Razer Logo and adjusting accordingly.
Also be sure that your audio settings on both headset and game are correct. Make sure that in COD you have it set to , but then set your headset to 7.1 (by pressing MAELSTROM, LOCATED AT TOP OF CONTROL POD)
To reset all settings, hold down the Razer logo for about 15 seconds.