Speakers Busted

I can’t control the volume of my speakers (Altec Lansing). I twist the knob and the volume remains the same. At random times of the day, the volume will suddenly jump to the right volume. There are no screws on the speakers, so I can’t open it. But hardware may not be the only problem. On my Windows XP, I do not see a volume control icon in the lower right corner of my screen no matter how many times I reinstall my audio driver.