What happens is essentially Windows registering the device instance in the configuration - the driver etc is already there, it just follows "new device attached

What happens is essentially Windows registering the device instance in the configuration - the driver etc is already there, it just follows "new device attached -> discover applicable driver from known installed set -> attach the driver to this instance of device". Newer Windows versions simply hid the behaviour, while windows 7 is the last one to not hide it.