Windows 10 (PowerPoint question)

I’ve recently installed Windows 10 and PowerPoint isn’t working well now. Ppt files are broken and it opens only those files that have pptx extensions. PowerPoint 97 and later versions are broken too. I thought about installing a PowerPoint Viewer, but it’s not convenient to open all presentations through a separate program (besides, I have lots of them archived on http://essaywriting.ninja so won’t be able to extract). They say downloads are available only till April, 2018 at https://www.microsoft.com/en-us/download/details.aspx?id=13.