First, let me warn you about file sharing over a P2P network...you are just asking for trouble. P2P file sharing opens your machine up to just the kinds of problems you are now experiencing...stay away from them. That being said, let's see if we can fix you up.
Open Control Panel and double-click on the "Sounds and Audio Devices" icon. Under the "Sounds" tab, select "Windows default" in the Sounds Scheme drop down menu.
Under the "Audio" tab, make sure that ADI 198x Integrated Audio is listed in the top two sections...if not, select it from the drop down menu.
Under the "Voice" tab, make sure the ADI 198x Integrated Audio is listed in both boxes...if not, select it.
Under the "Volume" tab, put a tick in the box to "Place volume icon in the taskbar".
Click "Apply" and then "Ok".
Now look down by the clock...is there a little speaker there? If yes, double-click on it and make sure there is not a tick in the box next to "Mute" and that the Volume sliders are all set to at least halfway.
Reboot...do you now have sound?THEN
....Please go to the Malware Forum
and follow the instructions at the top....Especially the Start Here
That will give you several steps that will help you clean up 70 percent of all problems by yourself...then post a hijackthis log in THAT
forum. Be patient, the Malware Forum is a very busy place and a two or three day wait is not unusual. DO NOT REPLY TO OR BUMP YOUR OWN LOG. If it shows a reply it may be overlooked as one that is being worked on.
If you are still having problems after getting a clean bill of health from the malware expert, please return to this thread.