Screeching sound occurs when recording, HELP!

Alright, here's the problem.

Whenever I'm recording audio or doing a voice test, I hear a loud screeching sound that comes through my speakers. The weird part is it happens regardless of whether my mic is plugged in or not. It still happens even when my mic is unplugged! So whenever im using a program like Teamspeak, Ventrillo, or even the VOIP on BF2, the people on my server hear the loud screeching sound but I cannot. Once agian this occurs regardless of whether I have my mic plugged in or not.
It's really weird because the loud screeching noise is usually microphone feedback but how can I have mic feedback when my mic isn't even plugged in? Also, even when I unplug both my mic and my speakers I know the problem is still happening because the recording bar and sound bar on my CM6501 sound config is at the max even though I can't actually hear it (because my speakers are unplugged) but as soon as I plug them back in I hear the screeching sound agian. I've tried turning off microphone boast and I've fiddled around with my sound config a lot but I can't figure this damn problem out. My mic worked fine on my old computer but than I got my new computer and ever since I have had this damn screeching problem whenever I record or try and use my voice with my mic.. or without it. Besides that though my sound works great. Also I just installed the latest driver for my sound card and it didn't change anything. I'm pretty sure all my other drivers are up-to-date. I don't think it's a mic problem because it happens without my mic too! I wonder... Do I have a defective soundcard?

I have a M2N-E SLI C-Media6501 Soundcard. Please someone help me fix this!!