Windows 95 extends the Windows 3.1 multimedia driver architecture by including support for Plug and Play configuration and device arrival or removal notifications. Although Windows 95 requires a supporting virtual device driver (VxD) to interact with the Configuration Manager, the implementation of the primary functionality of Windows 95 multimedia drivers uses 16-bit protected-mode code.
The term "virtual device driver" often suggests the concept of device virtualization, however, Windows 95 also uses VxDs to implement 32-bit "supervisor mode" or "trusted mode" code. For multimedia device drivers, VxDs serve two primary purposes: interacting with the Configuration Manager and managing hardware contention between Windows applications and MS-DOS applications.
Although it is not required, you may also decide to implement some of the core driver functionality in the supporting VxD and create a private interface from the 16-bit driver to the VxD.