i have an acer aspire 4741 notebook with a "realtek high definition audio" and a few months back i decided to update the driver
i went to acer's support site and realised the driver update they had for my model was way behind the the latest driver realtek had on their site. so i decided to download the latest one from the realtek site.
after install, the sound was playing alright but a few minuets later, i realised that even with my headset plugged in, the sound was still coming from the speakers and not the headset.
then i remembered a warning notice i had seen on the realtek site that their audio drivers
are "general drivers" and the best thing to do is to download driver updates from your system manufacturers site, as most computers come with customized audio drivers.
so i went back to acer's site and searched through their aspire notebook models till i found a realtek hd driver that was more recent than the one they had for my model. downloaded, installed and everything started working great again. when headset is plugged in, the sound comes from the headset and not the speakers.
so if incase, like me, you downloaded a driver from your driver manufacturers site, then perhaps you might want to try downloading one from your system manufacturers site to see if it solves the problem.
please this is just a suggestion and in no way a professional fix.