This will be a guide for setting up Virtual Audio Cable to isolate your audio channels. The main purpose of this guide will be for music playback through your microphone without playing back audio like Ventrilo.
First install VB-Cable This will add different channels for you to play audio onto.
Go to your audio settings.
Now set CABLE Output to listen to your default sound output (this will usually be labeled speakers.)
Now you just need to setup Ventrilo to run on your secondary audio line.
EDIT- Forgot to mention that you need to set your output device in Ventrilo to your new line, in this case CABLE Input.
Anytime you want to play audio through your mic you switch the input to CABLE Output, and when you are finished just switch it back.