Microsoft Windows Update was a part of Internet Explorer and you had to run it over and over, reboot in between, and patiently wait for each patch to download and install until the asset was up-to-date. Microsoft added a new compatibility registry key that must be set by an anti-virus vendor in order for Windows Update to continue functioning. Malware executing with the proper privileges could tamper with this registry key as well and revert an acceptable state to stop updates in the future.”]
Source: https://www.csoonline.com/article/3251803/a-patch-in-time-saved-nine.html