
Once it's checked, it seems to fix the problem.
Edit: It doesn't seem to fix the problem entirely. Audiodg still grows but much slower than before. It grows about about 50-80mb a day, so it's acceptable. I just restart the Windows Audio service to restart audiodg again once in a while.
Update: I have upgraded to Windows 7 and the problem seems to have disappeared. I suspect Vista is to blame.