Yeah you can do this. I use this program called
ISpy, its bascially a surveillance program which uses webcam.
1)Just download it, plug ur webcam in and add your webcam.
2)Then plug ur mic into your comp, enable playback volume so that you can actually hear your voice through your speakers.
3) go to control panel->sound->recording and enable stereo mix
4)Inside ISpy, right click the webcam and press edit. Under the first tab(camera), there will be microphone option. Choose stereo mix.
5)remember to off all the other survelliance options (motion detection, alerts and off all automated recording) also remember to change the maximum framerate in which the video will be recorded.
When you are ready, hit record in ISpy, play your MMO through itunes or something and sing along! It should record all audio coming out through the speakers together with the video of the webcam. The awesome thing about this software is that u can add multiple webcams and place it at different angles for multicam setup haha!
You can also just make ispy record only your microphone input if you intend to do some post production.
Hope this is of some use to you.
