Hi,
I like to thank you in advance for the help.
My Vista MCE HTPC is set up to run through a preamp/amp (dont know what it is really). Its a Vocal Pro and it has settings for karaoke and stuff like that. Then it goes into my receiver. All is dandy when I watch a movie/tv/music until i try out karaoke. I plug in the microphone and when its on, it has loud screeching noises which I assume is from the waves bouncing off each other, i dont know. Anyway, its really annoying and loud.
My speaker setup its two standing speaker on each corner of front wall with two satellite in each top corner on the back wall. And a center speaker in the front of the tv. The walls are dry walled, nothing special is done and the floor is oak.

Are you talking about feedback?

I think that's what it is called.

Well do you have the microphone in front of the speakers? Don't do that.

Otherwise, you could try gettings something like a feedback destroyer...