Hi All.I have a USB modem device. The modem driver is working in Windows XP.You know. I've rebuilded the source code to do the modem test in Windows Vista. (Windows Vista and Windows Server Longhorn x86 Checked Build Environment)Butthe Dialup Networkingdidn't work in Windows Vista x86 and x64.Ithad worked a few months ago in Windows Vista.As of present, it didn't work suddenlyin Windows Vista.After executing RasDial function, it showed up the error message as belows:The specified port is already in use or is not configured for remote access dial-out. (Error Code: 633)I checked communicating from the device by Dignosis Tool.The device is worked to reply for AT command. After processing IOCTL_SERIAL_SET_DTR in my driver, I found a cluethatIOCTL_SERIAL_PURGEhad been called suddenly from Dialup Networking in Windows Vista. But I don't know why.In Windows XP, it had never called IOCTL_SERIAL_PURGEduring a connection ofDialup Networking. It seems to be changed somethingin Windows Vista. Could you explain me about this situation?Regards.Taery.