Is there any way to disable this feature?

Disclaimer: I don't have a Bold. However, assuming that VAD is the same as on other BB's, just assign the Convenience Key that it's assigned to, to something else.

Since you didn't specify that you wanted to uninstall VAD, just that you want to disable it, just hide the icon and don't use it. Then, as mentioned above, assign the convenience key to another application.

Unless you meant something else.

That's exactly what I wanted. Thanks so much.