When the user selects a driver from the Installed Drivers list box, the Add Driver dialog box closes. The new driver becomes selected in the list box when the user chooses the OK button. The Drivers Control Panel application sends the DRV_INSTALL message to the driver if there is only one entry in the SYSTEM.INI file for it. (A driver receives the DRV_INSTALL message for its initial installation.) The Drivers Control Panel application can install up to four wave devices, four musical instrument digital interface (MIDI) devices, and ten media control interface (MCI) devices of the same type.
If the selected driver is not an installable driver, the Driver Control Panel applications displays a “Cannot Install” message. If the user chooses the Cancel button, the dialog box closes with no changes made.