Currently only Visual Studio 2003 is supported.
To do so go to Tools | Options | Administration where you will find a checkbox to enable or disable the Add-In:

Setting this checkbox registers the Add-In COM object and enables the Add-In in the Registry. Unsetting it unregisters the COM object and the Add-In reference in the registry.
You can also enable and disable the plug in through the Visual Studio .Net Tools | Add-in Manager menu choice. You can simply deselect the startup options to disable the plug in. However, note that this will not unregister the COM entry for the Add-in.
However, it's necessary to have a non-default keyboard scheme enabled in order for any application to be allowed to assign hotkeys in VS.NET so you have to ensure a non-default scheme is used in order to see the hotkeys. To verify whether hotkeys are used check the West Wind Html Help Builder menu under the Help menu and see if the Show Help Builder and Update from Help Builder show their respective hotkeys next to the menu caption.
If they do not follow these steps to create or select a new keyboard scheme: