In regard to the volume, try right clicking on the "Speaker" icon in the task bar and then click "Open Volume Mixer". Check to make sure nothing that you are using (including the main speakers) is set to be to low.
If that doesn't help you may want to go into the "Control Panel" and then "Sound". While on the "Playback" tab, select the speakers (one click only to highlight) and then click the "Configure" button.
In regard to the headphones, try them on another device and see if they work well or not. If you get the same problem, it is the headphones. If you don't, it may well be a bad jack on the laptop.