First, the hardware problem
This situation should be excluded first, whether using a speaker, or headphones, check whether the device is properly connected to your computer, and try reseating the audio cable.
Second, the system setup problem
This is a very complicated situation and there are a lot of possible causes, so let's take a look at the general resolution steps below.
Set sound-related properties
1, first into the Control Panel-sound options, in the Playback tab below should have speakers such devices, double-click the Open Properties window, in the Level tab, to keep the horn-like button for the normal state;
2, the same, if the microphone is not sound, enter the Record tab in the level of a column, keep the sound-like icon for the normal state.
Third, check the sound card driver is not a problem
Right-click the Start menu's computer options, select Properties, go to Device Manager, and see if there are any items with a yellow or red exclamation mark in the sound, video, and game controllers, and if so, try updating the sound card driver (Download the Driver Wizard to update automatically).
Check if the Win7 voice service is disabled
Right-click the computer in the Start menu, select Manage, go to the service option, and find a Windows audio to ensure that it stays in a startup state.