Sound Problem (Fustrating!!)

Gentlemen, Well, I thought some of you would know what my problem is, here it is. Earlier today my sound worked great, and it still does, yet something is with my mic. When I have nothing plugged into my headphone jack on my left speaker, i hear a slight buzzing sound. Sound strange eh? When I plug in my mic into the headphone jack on my left speaker (and the mic is unmuted), I still hear the buzzing sound. Really strange... Now when I mute my mic in XP Home Sound Control Panel, I don't hear the buzzing sound. Wierd.... This has happened before yet my mic doesn't work this time, as it worked last time when this happened... I'm not too happy with this. If anyone could help me it would be GREATLY appreciated... Keep Your Wings Level...Chanse Watson "CW"