107MB/s *network* file copying slowed to 16.5MB/s playing *local* media files. Why? Is there a way to adjust?

"The slow down is likely caused by the multi media class scheduler. Brute force is to disable the service. Mark Russinovich's has a blog entry with info on how to tell if it's the multi media class scheduler by watching the number of ndis packets per second get throttled. Some sites say to increase the tcp window size so you get more data per packet.

This is about vista, but seems to give the registry entry to tweak for the throttling.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\
CurrentVersion\Multimedia\SystemProfile\NetworkThrottlingIndex

A value of 0xFFFFFFFF will disable the throttling, otherwise it's the # of packets per millisecond. Restart is required. Microsoft has a support article KB 948066 that describes the key."

"Without knowing hardware specifics..

Seems to me that the network card hands off a fair amount of processing to the CPU - so when the CPU gets busy, the network card has less of a share to the CPU and is therefore being slowed by a processing constraint.

Also be aware windows 2008 and large packets have weird effects on some network hardware.We've found HP NC373 chipsets do not have processing grunt for Checksum & Large send offloading causing dropped packets, so have had to disable that feature."