Richard's computer sound system by Microsoft is having a problem where only the right channel is playing. Leo says that every cable should plug into something, so he should check and see if all his cables are seated. The cable that plugs into his computer could be failing. So try and replace the cables.
This system that Richard has is about 20 years old, so it may be time to get a new one. That model also has a USB connection option, which would be much better than the analog minijack. So he should try that. Logitech makes excellent computer speakers. Or he could go with Audio Engine if he wants a serious setup. They're more expensive but they are as good as his stereo. Bose also makes good ones in the middle range.