Thanks for your quickly answers! But my very important client demands support of Windows 2000 and XP only. I have very specific USB device and have written WDM driver (not audio) for it. My client demands support of waveAPI. Therefore, I need to translate waveAPI calls to specific IRPs for my device. I has looked in mmsystem.h and MSDN (and Google :) ), and I have written simple installable driver. However, I don't see any debug messages from my installable driver (I use OutputDebugString in driver and DebugView utility)! May be I have forgotten something and Windows does't use my driver?! Direct me in a right direction please! I have not enough information about installation of audio installable drivers and them internal structure... -- Igor Galchuk <ingvio@xxxxxxxxxxx> ****************** WDMAUDIODEV addresses: Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx Subscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe Unsubscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe Moderator: mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx URL to WDMAUDIODEV page: http://www.wdmaudiodev.com/