My internal Speakers are muted and when I go into System Preferences the mute button is check but it is grey, so it will not allow me to uncheck. In the sound folder it simply says "no output devices found". My computer remains silent in any situation.

because the sound preferences was greyed this means that you have to re install the driver for your sound card.The sound driver is corrupted insert the dirver into your CD room the run the driver for sound card..

Apple menu (top left) System Preferences > Sound > Output tab select the Internal Speakers
check your output volume and make sure the Mute checkbox is unchecked.
Plugin a pair of headphones. If you still have no sound. The sound board needs to be replaced, which is attached to the logic board. Meaning the whole logic board needs to be replaced.

Go to the Apple menu (top left) System Preferences > Sound click the Output tab at the bottom there is a Output volume slide bar, slide the blue upside down house all the way to the right (max volume) make sure the Mute checkbox is unchecked.

Your keyboard top case is fu.ked. Replace the top case keyboard and your sound will come back.
Have the Apple dorks do it if your still under the 1 year standard warranty or 3 years if you bought the extended warranty.

first of all change the play back set from head phone in the audio tab and see if there is mute option on on the speakers symbol on the system tray bottom right hand on the system if yes uncheck the mute

Go to the top of your keyboard. There is a button with a black sideways bell shape icon on it ( a speaker) (the f3 key)...probably four in from the left starting with esc. Toggle that on. It may be on the mute setting now. It should have waves coming out of it when it is unmuted. To the right of that button (two buttons to the right) is the increase volume control button, the (f5) key. Make sure the volume is up! If it is down all the way you will hear nothing and it will be also muted.
I am not sure why if you go into System Preferences (under the Apple icon) and scroll down to Sound and Output, the mute box cannot be unchecked. Perhaps using the function keys to unmute and increase volume on the top of the keyboard will help.

Plug in your external speakers then go to system preferences then sound when in the sound control panel go to the output tab and select the external speakers as the device for sound output and of course at the bottom of the control panel make sure that the mute check box is unchecked and turn up the volume. Hope this helps

Which version of the Mac OS?
You will need a sound output selected to be able to unmute the sound. Internal Speakers, Build-In Output should show in System Preferences :: Sound. You may have to "archive and reinstall" to get the sound driver, if say deleted or moved. If you can make an appointment at the Genius Bar of the nearest Apple Store. -Ken

hi
Go to Control panel > Sounds and Audio Devices > Volume. Check that Device Volume is at least halfway across the slider and that Mute is unchecked. Go to Advanced and make sure that nothing is mute. Go to Speaker Volume and set the sliders at least halfway across the slider. Go to Advanced, and in Speakers setup choose Laptop Stereo Speakers (if that's what you have). Go to Performance and choose Restore Defaults. Click Apply > OK

plz do inform if this has sorted out the problem
all the best
regards

Go to the system preferences from by clicking the Apple->system preferences menu. check the mute option is on or not. Also check the other options