Example #1 on KSStudio's help discusses this in detail. May be that helps. Shyam V. Narayanan -----Original Message----- From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Zou, Ying(Patrick) Sent: Thursday, March 04, 2004 1:07 PM To: Zou, Ying(Patrick); wdmaudiodev@xxxxxxxxxxxxx Subject: [wdmaudiodev] Re: usbaudio with sysaudio? Hi, I am testing some filter driver on some USB audio firmware. After enumeration, Win2K could find usbaudio device and usbHID. They are all listed correctly in device manager, but system will display "sysaudio: addFilter xxxxxxxxxxxxxxxxxxxxxxxxxxx failed". If I use media player to play a sound file, it will display "no audio hardware". so, anybody knows whey sysaudio will display such error messaage? where did I commit some thing? thanks pat/