I have 10 year old Harmon Kardon desktop speakers. My power went out and they were plugged into my laptop.
When the power was restored the speakers turned on still although the connecting wire didn’t have any power.
Did the power outage short them out? They are 10 years old but still that would have been a coincidence if they happened to stop working then.
To start out, unplug the HK speakers from your computer and plug some earbuds/headphones into the jack. It’s useful to know whether the speakers are getting an audio input and this is the least inconvenient way to see if the problem is in your computer or the speakers.
The other side of the troubleshooting equation is to plug something like an ipod or phone into the speakers. Any sound with that?
Also double check that your laptop’s volume settings haven’t been changed. Raise the volume slider in the OS and make sure there isn’t a physical mute/volume switch on the laptop itself. This has caused many people headaches.