I just wanted to speak in computer speakers through the computer's microphone. Is there any way to do it? Any software?
A simple and free way to accomplish this is by using yahoo voice chat having various chat rooms that will be empty or only have "bots" so you will likely have a fair amount of privacy, but it will accomplish what you wish to accomplish quickly until you can figure out a better way. Just position the mic near your speakers and also where it will pick up your voice and sing away.