Its a setting in your Realtek HD audio. You need to mute line in volume or playback volume etc (something along those lines). Go explore and test different things in it. Use ventrilo Test in setup with a little back ground music to test your results.
The problem is in your realtek settings for sure, however if you still cant solve the problem then plan B is to go a USB headset.
This is actualy a VERY common problem. Here is a post from Mxy ages ago about the problem
"This just came up elsewhere and it made me realize that I've never typed this in here before now ( Shocked ) so I'm "copying " it here:
If you're getting unwanted echo then you probably have one or both of the following two settings that need to be corrected:
- In Volume Control -> Playback: "Microphone" is enabled. Mute it.
- In Volume Control -> Recording: Assure that only "Microphone" is selected, not e.g. "Stereo Mix" (actual wording varies between diff sound cards.)
I suggest that you bring up both sets of slider panels with every item selected so that you can see what else might be the problem, and then go back to the (smaller, useable) slider set(s) that you want to usually see when you bring up the slider panel thereafter.... (Or just write down the names of the ones that were selected in each slider set at the start and put things back as they were when finished... except for the changes mentioned above that is!!! >Doh!< )"