I inherited old Altec Lansing ADA 745 speaker/sub woofer. They once worked beautifully with older desktop (XP Operating) and newer laptop with Vista operating system. Now, I only get the lowest volume...
If it works on another computer without any problem, then problem might not be with your speaker, it must be with the computer's probably with sound settings. I think it was working with your windows XP running desktop and your other laptop, but it doesn't work with another (new) computer. If so, could you please let me know the model and make of your new computer with the operating system installed on it? If the sound card on your new computer is onboard, then I will be able to find out the details about the sound card and it's related software and I would check out it's settings/features. But if in case the sound card's purchased separately and you installed it, then I would need that sound card details.
If my assumption is wrong and your problem is with your speaker, then I won't recommend you to get it repaired. If it's a new item and you still have the warranty unexpired, then that's another case, and so this would be your time to use the Warranty.
Let me know with the details mentioned above.