[JohnM]

Stange-looking graph indeed, Vaughan. If you select the "Impulse Response Controls" graph group in the top right corner instead of "Filter Adjustment" would be intersting to see what the response looks like, you can save just the graph by clicking on the small disk icon in the bottom left corner of the graph. The problem probably lies in the mixer settings for your soundcard, many features have no corresponding control in the Windows mixer - in particualr, some acoustic effect may be turned on. If you post some screenshots of the soundcard's mixer and whatever other control applications it has (maybe some effects control panels) we may be able to spot the problem from those.