I just built my first home pc. The mobo is an eVga. The case is a coolermaster centurion. The problem is this: there is a plate on the front of the case with usb/mic/head phones. I pluged them into the motherboard in the sound header. I can only hear out of the left side of the head phones. Did I do something wrong?

-All the mobo drivers are installed
-The mobo has ac' 97 audio
-The cord from the case says ac' 97 on it

The only thing I can think of is it is a loose wire or something?

The case wire also has one connector that says hd audio and also a bunch of single wire connectors. Did I hook it up wrong? My mobo says it has ac' 97. Please help - the front connectors would be so convenient to have for gaming.

See your mboard manual for the the pinouts and proper connections. On some mboards enabling the front connections disables some of the back connections [especially the mic/headphone (or line out) ones]; on others all of them are availble front and back. The wiring of the connectors from the case, and the wiring at the headers, are not necessarily standardized - the connectors from the case may or may not work with your mboard headers. If they don't, you may have to re-wire the connectors from the case to suit the headers. If it's just a matter of shifting the postions of wires in the connectors from the case, you can often unlock the metal wire ends and shift them to other positions in the connectors, or just remove all the wires with their metal ends still attached from the connectors and connect them individually.

here is the thing. Let's say it is the left side of the head phone that is not working. If I go into the windows sound mixer and turn the balance all the way to the left side then I can hear out of the left side but it is very faint. So the head phones are connected correctly I think. That is to say signal is getting to the left side, it is just not loud enough. What could be the problem?

If you are sure the connections are right, it is very unlikely there is anything wrong with your onboard sound hardware. Since you have sound on the right, there is nothing wrong with your drivers.
The most likely thing to go wrong is your amplified speaker connections, or in this case the connection to the headphones.
Try other speakers, or headphones, or test the speakers, or headphones, you have with other devices that the jack will fit in - e.g. cassette players, portable cd players. It is common for the wires inside the cable to the amplified speakers or headphones to break inside the cable, particularly near the plug that plugs into the sound card, or the jack on the front of the case, if anyone has ever pulled on the wire instead of the plug there to disconnect the speakers or headphones. You will either get an intermittant connection, or no connection at all - if it is intermittant, wiggling the cable around will sometimes result in your sound working normally. The wires inside the cable can be broken anywhere between the computer and the amplifier for the speakers, or between the amplifier and a speaker or speakers, or between the computer and the headphones. With a cheap amplifier such as used with amplified speakers, you may be able to hear the side that isn't working faintly if you turn the volume all the way up. It is also possible the amplifier in the speakers is no good on one side, but that's unlikely.

The other thing you can check for is settings in other programs that control sound besides the default one accessed by clicking on the speaker icon on the desktop toolbar - e.g. Winamp, Windows Media Player - anything that can change sound volume, or mute sound.

There are two types of audio out in sound cards.
1. Line out (which needs to be used with powered/amplified speakers)

2. Speaker out (which can be connected to hardphones or unpowered/unamplified speakers)

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Headphones not 'hardphones'.

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On the front of the case I plug the headphones into the jack that says headphones and I have tried this with 2 different headphones with the same result. Maybe it is then a broken case wire. I looked at the circuit board on the front of the case where the audio jacks connect to the wires and the connections look good. I think I give up on this one - I will just use the back of the case.

K I had just given up and then I tried one more time to plug my second pair of head phones in. Guess what? They now work. The difference? The front jack only seems to work if headphones are plugged into the back at the same time. Otherwise I get the same thing - audio on only one line.

I think the output in the back is really a line out and not a headphone jack. So I guess this makes sense why it works this way. They probably figure you are going to have speakers that are always pluged into the back. And then when you plug in the headphone in the back that probably cuts those speakers off and redirects the signal to the front. Well in any case it works now - JOY!

Thanks for the help Tubes and ham. You guys do a great job.

I meant:

"And then when you plug in the headphone in the front that probably cuts those speakers off and redirects the signal to the front"