anybody record there own music?

[G.Elias]

I don't record my own music though I have been known to remix a few.  Taking a great song and putting a personal touch on it can be very satisfying.  For any vocals I have been using a Blue Yeti condenser mic.  Works great for me.
A friend is trying to actually make music and when attempting to use my mic and his PC to record he get's his vocal's as feedback in the headphones.  Any way to eliminate this?  Or do I need to spend the money and get different equipment for this kind of thing?  If so what do I need to purchase to make this happen? (I'm guessing a Preamp-mic power, an XLR condenser mic, but I don't know what else or even a good brand)

Any help will be appreciated.  Thanks all!

Never tried recording anything with headphones on,i only have a cheap karioki mic taped to a chair leg next to my bass amp.it goes into a outboard soundcard where it gets recorded,is it just your onboard soundcard you are using?Never heard of this before,theres a lot of music production forums these days,maybe google your problem and see what comes up?