I had added Windows Vista RC1 in my system. It is entirely a new OS which I installed over XP. Now the system works quiet nicely. The drivers are updated. I am not getting audio in that. I use a microphone for voice chatting. It works, but due to some reason there is no audio hardware listed. I checked inside Device Manager and found the problem. The driver failed to work with Vista RC1. And along with that I will also need a proper codec pack that can fix the issue. From where can I download SigmaTel High Definition Audio Codec to make my system respond properly.