I can't profess to be any kind of a sound or laptop expert, but I may be able to help you troubleshoot some.
1. In your volume control, the wave volume slider should be all the way up, not the balance. The balance should be in the middle, which means that the volume is evenly distributed across the two channels of stereo output. Make sure you have gone to properties and opted to view all of the necessary volume controls.
2. Look about the keyboard of your laptop. Some laptops have keys with secondary functions as volume controls--my mother's laptop had these and after a while we learned that we were accidently hitting the key that made volume go down/mute.
3. Perhaps if you run a program that manages your audio, you might see if there are any off settings in it.
4. Check forums dedicated to people that have bought the same laptop as you. Especially look for people with the exact same problem as you.
Best of luck to you.