this is the circuit im working with
http://www.ehow.com/how_4683349_wii-microphone-gh-world-tour.html

its made for a dynamic mic, so it has no power.

would I be able to connect the 5 volt line from the usb to the mic line and have it power an electret mic?

also, would i need a component inbetween to prevent the current from flowing back into the circuit?

 

Pulling 5v off USB is easy, but you need to make sure that your current draw wont kill your pc. Give us some more info.

What are the specs of your mic?
You may need further components, but we have to start with the proper parts. Do you have a datasheet or a link to info on the mic?