Problems with the outputs of the built-in sound card?

Question

Audio

An ordinary computer with a built-in sound card, there are 2 green outputs - behind and in front of the system unit.
Everything was working fine, but after reinstalling Windows 7, there was a problem.
The speakers connected to the connector on the back of the system unit began to work only if headphones were still connected in front, for example. But the sound only plays through the output at the back. You poke the plug from the connector in front - the sound stops playing, in the windows soundbar tray it is displayed that the sound is working.
What could it be? drivers? do you need to set something up?
Realtek High Definition Audio
Realtek AC97 4.05
Elitegroup A75F-M2

Answer 1

So, share the system configuration, I will give all the links.
Realtek codec - click Driver
version - click
Mat. board \ sound card - click
How to write - I'll tell you what and how