Well, so far I've tried msconfig and regedit's find feature (even checked through the hkey/.../run key manually) and have found nothing that directly states "topsearch.dll". I know it's a by-product of some adware/spyware that made it onto my machine with KaZaa, though the uninstallation in Kazaa directly resulted in this message always popping up. Ultimately I'd love to find out where this dll is being called from (as you've stated, which app is the key) so I can remove the cause and fix the symptom.