HELP! Need to convert 1 channel audio to 2 channel audio!

[i am x]

Someone PLEASE help me! I have a movie file in which the audio only came out on the left channel. I need a learn how to convert the audio so that it comes out on BOTH channels. So far, I demuxed the audio from the video with TMPGEnc Plus. The resulted audio is an .mp2 file. From this point, how do I convert it so that the resulted .mp2 has sound on BOTH channels? ANY help would be appreciated! By the way, I DON'T want to change the file to .AC3 format. I want to keep it as an .mp2. I just want to convert it so that the sound ends up coming out of both speakers instead of one.

[Tommyknocker]

Launch Gold Wave and load the original video. Copy the channel with the audio and MIX it with the channel that needs the audio. save as a wave file. Go back to TMPGEnc Plus! and load both the original video and the new wave file. Select ES (Video + Audio). You output files should be the same as before, but now the new mp2 file has audio on both channels.