Not a valid Office add-in message at MS Outlook startup

I recently had a motherboard meltdown on my primary home computer and I had
to switch to an older desktop computer until I can get a new one. The older
PC is running Windows 98 with Microsoft Office 2000 Small Business. The
first thing I did after getting the cable connection working was install and
update Norton's AntiVirus and do a full disk scan. I then downloaded and
applied all the operating system and Office service packs and critical
security updates. Everything seems to be working fine but when I start
Microsoft Outlook I get the following message.

C:\WINDOWS\Applications Data\Microsoft\AddIns\ is not a valid Office add-in.

The AddIns subdirectory had no files in the directory. When I click on the
[COM Add-Ins...] button on the Tools/Options/Other/Advanced Options popup I
get the same message as I got at startup. I've tried a number of things like
trying to install add-ins and copying .dll files to the directory but nothing
gets rid of the message.

Can anybody help?

I will be getting a new PC to replace the one that died but I want to use
this old system as a standalone email server for my not too computer savvy
family. It's only a 450 Mhz system so I'm not planning to do anything but
keep the antivirus software up-to-date.