One of the nice things about Windows is that there are so many third-party programs available. If you need a word processor, you can use Microsoft's Word, or the free LibreOffice, AbiWord, or any one of dozens of other options. Don't want to use Internet Explorer or Microsoft Edge? Chrome and Firefox are a download away.
Even better, Windows lets you choose your default programs. That way when you click a link, or double-click on a document, photo, video file or music file, it opens in your program of choice. Unfortunately, Windows 10 has decided it doesn't want to play nice with third-party programs anymore.
The problem started with the latest round of Windows updates, specifically patch KB 3135173. After it installed and the computer rebooted, a number of people discovered that all their default programs and file associations had been reset.
The Windows 10 Action Center listed a string of error messages saying that there was a problem with the third-party program or file type and it had to reset. The reset, naturally, routes everything back to Windows programs like Microsoft Edge, Windows Photos and others.
The update also wiped out third-party options from context menus. So, if you right-click on a file, you won't see any of the options for opening it or using it with your third-party programs.
Even worse, users who tried to put their defaults back to the way they were have found that Windows 10 will show an error message and reset it again. So, was this a bug or is Microsoft declaring war on third-party programs?
Fortunately, Microsoft just started releasing notices explaining what's in the updates, a practice it had stopped for Windows 10 updates. So, we know that update KB 3135173 isn't actually supposed to be messing with the default program settings. That means this is almost certainly a bug and Microsoft will be releasing a fix.
Unfortunately, there isn't much you can do in the meantime. Uninstalling the update will let you set your own defaults, but Windows 10 will just try to install it again unless you do some high-tech trickery that isn't recommended for most users.
Hopefully, with this being only the latest in a string of problematic updates, Microsoft will take a hard look at its mandatory update policy. It's not a bad idea for security updates, but for program and non-essential updates, it would be nice if users had some control so they didn't fall victim to problems like this one.