If you upgraded from Windows Me to Windows XP, starting Outlook 2000 may produce the following error:
The add-in "C:\WINDOWS\SYSTEM\ACTEXT.DLL" could not be installed or loaded.
When you press OK, Outlook opens.
NOTE: ACTEXT.DLL is a 3rd party extension, installed by the ACT! software, that provides access to the ACT! address book.
To workaround this behavior:
1. Close all open programs.
2. Locate Extend.dat, a binary file that Outlook uses to cache registry entries for 3rd party product extensions. It is likely located at %USERPROFILE%\Local Settings\Application Data\Microsoft\Outlook\extend.dat.
3. Rename the Extend.dat to Extend.old.
4. Restart Outlook. A new Extend.dat is automatically created.