busTRACE Technologies has developed a simple utility that allows you to view which filter drivers are specified for the Disk and CD/DVD devices on your computer. This applet shows you those filter drivers that are specified in your registry. They may, or may not, be actually running. That is dependent on the driver itself.

This is a useful diagnostic applet for those users who have a need to determine which Disk/CD/DVD filter drivers various 3rd party applications, or Microsoft itself, have installed on your system

Windows 2000/XP provides a layered approach to device drivers. That is, a device driver developer can write a filter driver that sits above or below a function driver. In our case, we are checking for filter drivers above and below any Disk Drives and CD/DVD devices detected on your system.

A developer can install their filter driver to filter I/O activity for all Disk/CD/DVD devices (e.g. class filter), or on a per device basis (e.g. device filter). The driver can be specified as a lower filter or upper filter. IRPs (I/O Request Packets) are sent down the I/O stack, and processed by these filter drivers, in the following order:
· Upper class filters
· Upper device filters
· Function driver
· Lower class filters
· Lower device filters
· Bus driver/filters