"Multimedia Class Scheduller" service is what caused me my lag.
Just disable the service.
windows sound is dependent on this service so you will then need to;
run regedit,
then find HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Audiosrv\DependOnService
double click on it and remove MMCSS from the list
reboot and play lagfree.
I searched for HOURS and HOURS and HOURS to fix my lag issues;
This fixed it for me and dropped my ping in fear combat from 180 to a solid 50