A newer version of Microsoft Office (2016, 2019, 365) may reject a DLL compiled for Office 2000 due to security enhancements like Protected Mode or disabled legacy COM glue.
The genuine udcofficeaddin2000.dll is not a Windows system file and is not inherently malicious. However, malware has been known to use similar naming conventions (e.g., udcofficeaddin2000.dll could be a disguise for a keylogger or backdoor). udcofficeaddin2000.dll
If the DLL was damaged by a system crash, Windows can often repair it automatically. A newer version of Microsoft Office (2016, 2019,
The file's registration in the Windows Registry (under HKEY_CLASSES_ROOT or HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Addins ) can become corrupt due to improper shutdowns, malware, or failed updates. or failed updates.