Sometimes, I really like the simple problems.
This has only happened to me 2 or 3 times, but it can test your troubleshooting skills.
Laptop plays no sound.
Depending on the laptop manufacturer, the control panel sound options are either not muted, or its muted, and the mute tickbox is greyed-out (and cannot be un-muted).
Updating drivers has no effect.
I eventually do what I should have done very early on: carefully examine all the buttons and switches along the front, sides, and top of the laptop.
I usually find a front or side button (annoyingly camouflaged black-on-black, with either black writing, or writing that is slightly raised), that will quietly mute the sound (or worse, directly disable the speakers, so that windows is none-the-wiser!).
Its also possible to mute using blue “Fn” button, but thats usually a lot more obvious.