no sound

Try this.

Go to "System Preferences", click on "Sound", now at the very bottom at the slide bar that says "Output volume"

to the very right make sure that the "mute" box is NOT checked. Also where it says "Play sound effects through" click the arrows and make sure that "Internal Speakers" are designated. Make sure to look under each tab click at top; "Sound Effects", "Output", "Input" that "Mute " is not checked in each item.

Often a SMC reset can cure that.

Resetting the SMC (System Management Controller) on Intel-based Macs:

http://support.apple.com/kb/ht3964 and

http://support.apple.com/kb/HT1237?viewlocale=en_US

Resetting your Mac's PRAM and NVRAM:

http://support.apple.com/kb/ht1379

If you are using a Wireless Keyboard:

http://support.apple.com/kb/TS3273