Have you tried updating the driver(s)?
You'd go into Start / Right click on My Computer / Properties / Hardware tab / Device Manager button.
Then look for a yellow mark left of problem devices, and try to update their drivers online from right there within Device Manager. Probably look in (click the + to expand)
"Sound, video game and controllers" and also inside "System Devices".
Anywhere you see a yellow mark is a problem. Try to update drivers.
As long as you're sure all your electrical connections are good, and volume control is on, that's about all I can think of.
One time I had a "no sound" problem and everything looked good. But I eventually discovered that a "mute" checkbox was ticked in some other player I rarely use, somehow overriding the Windows volume control.
So that's my last idea, go through any software players and make sure none of them are set to "mute" or their volume turned all the way down. Nero Player, VLC, Classic Media Player, RealTEk AV Rack, whatever else you may have on there.
Good luck. Maybe someone else will post in here with other suggestions.