Need more information.

First, get a set of stereo headphones and plug them into the back of the computer. Unplug the cable that you added that goes to the home stereo. Plug the headphones in there. The earphones/headphones from a Walkman will do just fine.

Play music and verify that you are getting stereo out of that computer connector.

If you do not get stereo the problem will be with the computer.
If you do get stereo the problem is with your hook-up to the home stereo.

I assume that the latter will be the case.

Now look closely at the plug on the headphones and notice that the plug is made up of three elements. Check the cable that goes to the home stereo, is that plug also made up of three elements? It should be.

Check the other end of the cable, does it have the exact same type of plug or does it have two RCA type plugs?

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