I have Realteck HD audio on my computer. Recently, I took my computer in for repair because it wasn't shutting down and they fixed that issue, but now this one has come up. They updated a bunch of drivers, including the bios, and I'm positive the Realtek driver is up to date because I downloaded it myself.
When I get to my desktop the audio icon in the lower right hand corner says there is sound, if I open the Realtek audio manager the digital output port is highlighted on the right hand side. If i plug anything into the headphone jack, speakers or headphones, nothing registers. Even when I use the option withing the audio manager and check the box "Disable front panel detection" the speakers come up, but there is still no sound coming from them.
I'm pretty sure this is not a hardware issue (motherboard, sound card) because the sound was working perfectly before they fixed the shut down problems. I've even gone into the BIOS and made sure the audio/front panel are enabled.
Try right clicking the speaker button on your taskbar, and select playback devices. Are there multiple speaker or other outputs? If so, try selecting another one to be the default by right clicking on them, and selecting default for both device and communication device.