Define "miniplug". I'm venturing you refer to the size of a headphone jack, not a midi plug?
They make devices to convert large switches (hooked via "miniplug") to USB format for people with impairments, but that maps keyboard commands to specific jacks on the device. I have one laying around, it's a donjohnston.com piece of equipment.
What you're looking to do, however, is find a way to bind input to a "Direct Input" method for ventrilo. Usually gaming adapters (controllers, joysticks, etc) would be more appropriate, but you still need to convert it over to a format the system will accept. Ventrilo supports non-keyboard binds, handled through Direct Input from any DirectX compatible device.
Unfortunately, your purchase of the tap chat was, well, retarded:
Quote:
Please be informed that Creative do not officially claim to support 3rd party game and communication software. The WoW Tap Chat is designed for World of Warcraft game. However, for communication software such as Ventrilo, it can still be used as a mute/un-mute foot switch as long as the Tap Chat is configured for that purpose using the Audio Control Panel.
Unless you can bind it as an input that isn't a "keyboard replacement", you should really just look into usb human interface devices that support that, instead of reinventing the wheel.