I just re-assemble my computer and speakers and my speakers is not working now. I am not sure if I have left a plug out. Should something be plugged into the 'Audio In" slot?

These are analog speakers and do not need a driver. First, make sure they're plugged into the speaker/headphone jack and not the microphone jack. Second, make sure the computer's sound output is enabled and set the headphone/speaker jack. Third, verify that the sound output is working by plugging in a headphone set or a different pair of speakers. If the computer sound checks out, the speaker cable is bad or the power supply is not working.

Something must be damaged or in need of cleaning.

This is pretty easy to troubleshoot. First plug something else into the speakers to make sure they work. (cd player, phone, gameboy ect.). If the speakers don't come on make sure they are getting power. There should be a light on the speakers to varify they are getting power. If the speakers do work when you plugged them into something else, plug them back into the computer and make sure you are plugging them in the right portal. A common mistake is plugging them into the mic jack. Look for a small pair of head phones next to the jack on the back of the computer. Plug them in and go to your volume control on the bottom right of your computer screen. Turn that up. This should fix you problem...if not, you may have an issue with your computer.

Did they ever work or are you trying them on a new computer? They don't need switching on you just plug the plug into the audio out of your sound card or motherboard, make sure the mute button isn't selected on the inline remote. Play an mp3 on your computer, make sure the volume on your computer is turned up, plug in another known working set of headphones or active speakers make sure you can hear the music, then plug out those speakers and then plug in the headphones. Do they work when you try that?

control panel sounds and audio devices,audio you should find something there

Open the "Volume Control" applet & make sure the "Balance" setting is set in the middle of the scale. This way sound will go out through both speakers.

if there's buzzing coming out, there's probably a rip in the actual speakers. Something is torn on the inside thus the weird buzzing noise.

Unless it was a zzzzzzzzz...... noise then there's probably some sort of interference. Possibly cellphone close by, or some other magnetic thing to create that annoying sound.

Most probably there is a problem in the cable or plug.

I think I had a similar problem. My speakers were brand new and after a while I lost my front left and rear left speaker. I'm not sure about you guys but after fiddling around with the settings it worked after I changed the "S/PDIFoutput sample rate" from 48 to 96 khz. I have no clue what I did, but it worked for me. I am running logitech something or rather speakers with VIA HD audio deck drivers

Same issue showed up for me today very randomly...

HD comes on and off for no reason and sound cuts in and out. This fix worked for me:

1.Disconnect the left speaker from the sub woofer.
2.Take the 4 screws out on the bottom of the left speaker. (They are under the rubber matting you can just poke holes through it)
3. Remove the bottom plastic assembly from the speaker
4. Cut the 4 wires to the headset chip. Careful not to cut any others to the speakers themselves!
5. Unscrew and remove headset plug chip
6. Reassemble and plug left speaker back into sub woofer.

No more HD issues =)