Like he said... use the "Line In" on the back of your computer... you don't even really have a soundcard... AC97 is just a codec used mostly by onboard sound chips that are built right into the motherboard.
But in order to record anything, you have to tell Windows where you want to record from. Assuming you have a little "speaker" icon in your Windows task bar, just double click on that... then click on the "Options" menu at the top and click on "Properties". Then you'll see a selection button where you can chose either "Playback" or "Recording"... Choose "Recording". Below that, make sure that "Line In" has a check in front of it, then hit "OK". At the bottom of the window, you'll see that one of your recording devices will have a check below it. (you will prolly see "Microphone", "Wav", "CD Audio", "Line In", etc.). Make sure that you put the check under "Line In". That tells Windows that any application that records will get it's source from the "Line In" instead of the Mic (or any other device).
Try that and see if that fixes it. The simplest way to test your recording source is to use Window's built in Sound Recorder. That will always record accurately from the default Windows recording source.
WATYF