Universal Serial Bus (USB) protocol is very complex. So the USB support software present in Microsoft® Windows® operating system family is also complex and provides a layered architecture where the system-supplied and vendor-supplied user- and kernel-mode components can be involved in communications over USB. Transactions performed over the USB are basically initiated by the user applications which communicate with the operating system by calling Windows API functions which in turn interact with appropriate device drivers providing access to a USB device through standard and vendor-specific interfaces.

What do you do when you want to know what is going on inside the Windows USB subsystem? What USB drivers are used to connect various peripheral USB devices to a computer? What I/O requests, support routines, structures, and interfaces the core components of the Windows USB architecture use to communicate with the USB devices? What you need is a Software USB Protocol Analyzer.

Analyze and Realize USB Protocol!
USBlyzer is an easy to use Professional Software USB Protocol Analyzer for Windows, which provides a complete yet simple to understand view for monitoring and analyzing USB Host Controllers, USB Hubs and USB Devices activity.