Aha! I've discovered the source of my dreaded Outlook 10 warning issue.
Anil was right in fingering ICQ/Outlook integration. I hadn't installed it, specifically, as I had on my other machine, so I didn't think it was on here. Turns out, it's installed automatically when you install ICQ 2000b and you're running Outlook 2K. And the damn warning happens even if you don't have ICQ running or the ICQ toolbar in Outlook showing. Now, to get rid of it without getting rid of ICQ? (Or, even better, keep it, but tell Outlook to not warn me about it. I kinda like the feature.) Hmmm...
Anil was right in fingering ICQ/Outlook integration. I hadn't installed it, specifically, as I had on my other machine, so I didn't think it was on here. Turns out, it's installed automatically when you install ICQ 2000b and you're running Outlook 2K. And the damn warning happens even if you don't have ICQ running or the ICQ toolbar in Outlook showing. Now, to get rid of it without getting rid of ICQ? (Or, even better, keep it, but tell Outlook to not warn me about it. I kinda like the feature.) Hmmm...