Speakers do not register themselves as a device. The interface to the speakers is the sound card. Whether this is an add-on module or part of the motherboard, you need sound drivers for it. Make sure you have these installed. You can search for new hardware to get this done automatically. I would recommend Uniblue software which you can download from the internet if you can't get this working. Make sure you back up all your drivers before overwriting any by new ones.
Answers & Comments
Speakers do not register themselves as a device. The interface to the speakers is the sound card. Whether this is an add-on module or part of the motherboard, you need sound drivers for it. Make sure you have these installed. You can search for new hardware to get this done automatically. I would recommend Uniblue software which you can download from the internet if you can't get this working. Make sure you back up all your drivers before overwriting any by new ones.