Flayed

I recently purchased a new headset (Plantronics Audio 370) and tried to just plug and play. The outbound sound quality and volume level is amazing, and I was happy to hear it. Then, once I tried to go into Ventrilo and test the mic out, I realized I could hardly hear it at all. The only way I could get anything out is by turning the mic boost up to +40db and screaming into the mic with every volume level maxed. Even then it only came out as a static filled whisper. I updated drivers (Sigmatel Audio, onboard my Intel DG965WH) and that did nothing either. I tried absolutely everything I could think and tried many things I found from googling. Nothing worked and im stuck between a rock and a hard place of what to do. My old USB headset works perfectly, and this one is a 2-prong input to my rear jacks. I don't think my jacks are bad or anything because I did have an old headset that worked perfectly in the same jacks. Can anyone help?