|There is no sound control in Windows, or whatever operating system, that can disable the sound to the regular speakers without doing the same for the headphones.|
The headphones jack on laptops and netbooks has a mechanical switch inside of it. It's supposed to disable the sound from going to the speakers built into the laptop or netbook whenever you plug a plug (on a cord) into the headphones jack.
If you have plugged into the headphones jack a lot, it's common for that mechanical switch to malfunction. You could try plugging a plug into the headphones jack, wiggling it, then pulling it out, or just plug in the headphones and wiggle the plug, that may get one or both speakers to stop producing sound when you plug in headphones, but the only real solution is to replace the headphones jack - that's an item frequently replaced by laptop repair places.
If this is on a desktop computer, plugging in headphones usually does NOT disable the output to regular computer speakers from producing sound, because the headphones jack usually does NOT have a mechanical switch inside of it.
Turning down the volume on the regular speakers themselves to zero, or switching off the power on the speakers themselves if it/they have a switch or button, or unplugging your regular speakers from the computer, or unplugging the power adapter to the speakers, when you're using the headphones, are ways of doing what you want to do.
NOTE that SOME regular speaker pairs have a headphones jack on one of the speakers. If you plug headphones into THAT jack, it probably has a mechanical switch inside of it that will disable the regular speakers (only that pair) from producing sound when the headphones (or whatever) are plugged into that jack.