Part 1.
Goto start menu>right click Computer>Manage>Services and Applications>Services then search for Multimedia Class Scheduler.
Switch startup type to Disabled. (Startup type: "Manual" does not work)
Part 2.
Goto start menu type Regedit in search push enter then locate
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Audiosrv\DependOnService
Right click Modify and remove MMCSS from the list then click ok.
Reboot.
Thanks to Waymon in the
Counter-Strike source lag/choke thread.