Are you looking to connect it to your computer or are you planing on using it as part of your home theater system? you can buy a converter to go from the stereo jack to RCA if thats what your looking for.
Yes its the uninstall here that will help you if its the drivers thats the issue. Just pop out to your MOBO manufacturers site and they should have the latest drivers available.
im assuming you have the mic connected to the onboard audio jacks then it would just be the drivers for your onboard audio these you can find in device manager. also if your mic came with any software uninstall that as well
When you change out CPU's and motherboards you most often have to reinstall windows. Did you do a clean install or just pop in a disk and hit the upgrade button?
Did you do a fresh install of windows after you changed out the mobo and processor? You say your not sure if the issue was present prior to the change of hardware? Or did you do all those things after the problem first happened?