I'm having some odd issues with my sound card on Windows 7. For some reason, my built-in speakers are not working when running the laptop normally (i.e. nothing plugged into the line in/line out jacks).
However, when I plug in headphones into EITHER the audio jack or the mic in jack, the built-in speakers suddenly start to work.
When the headphones are plugged into the microphone jack, the speakers work, but the headphones do not. When plugged into the audio jack, both the headphones AND the speakers begin to play sound simultaneously.
When using headphones with a microphone and plugging headphone and mic jack where they correspond, the headphones work as they should and the laptop speakers mute.
Interestingly, when I am in Realtek HD Audio Manager, when nothing is plugged in, it registers that there are headphones plugged in. When I plug something into the audio jack, the headphones icon disappears, and the mic in jack is lit (which disables my built-in mic).
Also, right now I cannot recall if in the Realtek Audio Manager the jack's icons had a particular order, but now it seems they are switched? I mean, topmost is headphones and lower one is microphone, while in the computer it's otherwise, headphones are "closer to you" than the mic... I don't know if my explanation makes any sense.
Anyway... I've tried many solutions to no avail. Right now I will try to run Linux Mint from a usb to see if the problem persists, if so it could very well be a hardware problem.
If I were to guess I would say that the problem is with the audio board. You can take the laptop apart and remove the audo board cable to see if your speakers will magically start working. If they do then just replace the board.
If they don't then it would be the fault of the motherboard. You can buy a cheap hard drive and test with a different operating system to see if drivers are the culprit, but more than likely it's a hardware issue. If you figure this out keep us updated.
To test things out you could try to uninstall the RealTek drivers so Windows should start using it's own default drivers. Just to test and see if anything changes. You could also try some of the drivers from here: http://support.asus.com/Download.aspx?SLanguage=en&m=Audio&os=30 (Scroll down until you find a RealTek driver).