Audio disappeared

I need a little help. I was watching a movie on my computer and about 15 min in the sound disappeared. It is still showing the device working properly. I tried reinstalling the driver but it didn't help. I have recently moved and the computer was not used for about 2 weeks but worked fine for the last week. Could it have anything to do with the battery located on the mobo? The system is pretty old and I don't think the battery was ever replaced. After that happened I used my other computer which is identical to the first one and this one turned off after about 5 minutes but after restarting worked fine.
Any ideas or suggestions would be greatly appreciated