Registering a Dll Returns 0X80020009 Error

For Windows Vista/Windows 7 users: Click Start>All Programs>Accessories, then right-click on “Command Prompt” and select “Run as Administrator” Type in the following command exactly as you see it and press ENTER. secedit /configure /cfg %windir%\inf\defltbase.inf /db defltbase.sdb /verbose Wait for the command to complete, it can take some time so please be patient. Once the command has completed, try to register a dll file again.

For Windows Vista/Windows 7 users: Click Start > All Programs > Accessories, then right-click on Command Prompt and select Run as Administrator.

Best method I have found is to open the PowerShell ise with administration rights then cd to c:\ and insert your command, for example

regsvr32 "c:\Program Files\Windows Media Player\wmpband.dll"

For Windows Vista/Windows 7 users: Click Start > All Programs > Accessories, then right-click on Command Prompt and select Run as Administrator. Then type: regsvr32 filelocation\fileName Then you see that file which generate error is loadded successfully.

I had a similar problem with our Office COM addin. Visual Studio 2019 could successfully build the C++ code, but the registration failed with the above error code.

Solution was: Some files had a "wrong" file encoding (UTF8-BOM) instead of (UTF8) and after I changed the file encodings everything worked as expected.