fix: Error code 80240016 when installing Windows Defender definition update
When running the free online Windows Live OneCare antivirus/maintenance scanner (available as an ActiveX control hosted in a webpage – for Internet Explorer only), you may notice that Windows Update can’t install Windows Defender definition updates, saying that Windows Defender is installing other updates at that moment.
This message is misleading, just close the Windows Live OneCare webpage and try Windows Update again. It will now install definition updates. Then you can proceed by launching the Windows Live OneCare online tool again (or if you prefer wait for the scanner to finish, then try Windows Update again).