Antivirus without updating
If you run into this problem and you want to get the program back, just reinstall it.
In most cases, this will involve re-downloading the program from its developer’s website.
This allows you to roll back to the previous build of Windows 10 if you have a problem.
However, if you’ve removed old Windows installations using Disk Cleanup or manually deleted the folder after the upgrade, it won’t be there.
In some cases, people even reported that it removed PDF viewers and antivirus programs (perhaps outdated ones). In fact, Microsoft specifically declined to comment when asked about this by Venture Beat.
Confusingly, it seems like the Windows update removed these programs from some computers but not others. We also haven’t seen them issue a statement to any other media outlet or a blog post on the subject.
Instead, they’re more like upgrading to an entirely new version of Windows.
When you install a major Windows 10 update, you may reboot to find some of your programs missing.