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Some other program may have tried to grab those files. you can find out which one in the registry, but if you have already fixed it no problem.
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Some other program may have tried to grab those files. you can find out which one in the registry, but if you have already fixed it no problem.

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Generally this does not happen by itself. &nbsp;On the user machine involved:<br />
<br />
1. Scan fully for viruses and malware.<br />
2. Make a new, test, Windows User profile (Account) using Users and Groups. &nbsp; Test file association in the new Windows Account
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Generally this does not happen by itself.  On the user machine involved:

1. Scan fully for viruses and malware.
2. Make a new, test, Windows User profile (Account) using Users and Groups.   Test file association in the new Windows Account

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A PDF icon loses its program association, I resolved the problem by creating a new PDF file then configuring it to open with Adobe Acrobat.<br />
What can cause Windows 10 to disassociate excel and PDF files with programs designed to open them?
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A PDF icon loses its program association, I resolved the problem by creating a new PDF file then configuring it to open with Adobe Acrobat.
What can cause Windows 10 to disassociate excel and PDF files with programs designed to open them?

What can cause Windows 10 to disassociate excel and PDF files with programs designed to open them?

Windows 10 is a personal computer operating system featuring the "universal application architecture" (UAP); apps can be designed to run across multiple devices with nearly identical code, including PCs, tablets, smartphones, embedded systems, Xbox One, Surface Hub and HoloLens. Windows 10 also includes a virtual desktop system, a window and desktop management feature called Task View, the Microsoft Edge web browser, support for fingerprint and face recognition login, voice-based search (Cortana), new security features for enterprise environments, and DirectX 12 and WDDM 2.0 to improve the operating system's graphics capabilities for games.

Windows 10

A Portable Document Format (PDF) is a file format consisting of an electronic image resembling a printed document and can be viewed, printed, and electronically transmitted. PDF files can store various types of data, including formatted text, vector graphics, and raster images. The page layout defines the location, size, and shape of each page and each item on the page. The information looks the same no matter what device or program is used to open it.

This topic area includes legacy versions of Windows prior to Windows 2000: Windows 3/3.1, Windows 95 and Windows 98, plus any other Windows-related versions including Windows Mobile.