The screenshot shown to the right illustrates the issue. The initial section showing 38-42% network utilization is the network file transfer being conducted without Window Media Player playing back audio. The immediate drop-off in speed to about 9% network utilization is what occurs after playing an MP3 file located locally on the machine in Windows Vista. Closing WMP allows the transfer to resume at full speed and as said before, this issue is not present in other multimedia applications like iTunes.

There is a workaround that has been discovered by geek Courtney Malone. It involves a simple registry edit which can be done by following these steps…

• Open Registry Editor by using keystroke “Windows+R” and typing “regedit”
• Navigated to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AudioSrv
• Edit the value of “DependOnService” by double-clicking the item
• Remove the line referencing “MMCSS”

What you’re accomplishing here is disabling the “Multimedia Class Scheduler Service” which is designed to give multimedia and mission critical tasks priority on the network. This is a standard Windows service, but we can’t simply disable it by opening the Management Console Snap-in because it is linked to Windows Audio (which of course controls all sound on the machine). This workaround will solve the issue, although Microsoft has added a bit of control for the end-user over how aggressive MCSS will be if you’d like to keep it around. You can read about that here.