The amount of threats that we can find on the internet are many and varied. Sometimes it is enough to download a file so that your Windows computer ends up infected with a virus that, for example, changes all the extensions (formats) that prevents you from opening them correctly due to said extension change.

Related: How to open multiple programs at once in Windows 10 with one click

The extension of a file in Windows 10 is the indicator that allows the operating system to identify the program with which the file can be opened. If the program to which a file extension corresponds is not installed on your Windows 10 computer, this file will not be able to be opened or it will not be opened correctly if a compatible program is not used.

Some of the viruses that can be found on the Internet attack precisely this link between files and the programs that can open it. Its purpose is to change all or most of the file formats stored on your computer so that the appropriate application or program cannot be found to open it.

As we have mentioned, changing the file extension implies changing the format but also the file icon. In general, the files show the icon of the program capable of opening it, so if a virus changes this file format in Windows 10, the icons of these files will also change to those of programs with which you will not be able to open them.

Sometimes, it is possible that this problem is not due to a virus but to a misconfiguration of the default programs to open depending on which files. However, if this happens to all files, it is most likely that it is a virus, so the first thing you will have to do is scan your Windows 10 operating system with your antivirus program.

If the scan is successful, finding and removing all the infected files that caused the problem, then it is time to reset the default association so that these files can be opened with the specific programs.

Having said that, below we show you step by step how to solve the problem of changing the extensions of all the files on your Windows 10 computer:

Fix: All file extensions changed on my Windows 10 computer.

Method 1: Reset Default Values ​​in Windows 10 Settings

Go to the settings using the keyboard shortcut: Windows key + I

Once here go to: Apps> Default apps.

On this screen you will have to scroll down until you find the option: Reset the defaults that Microsoft recommends.

Next to this option you will have to click on the button:Restore.

Method 2: Delete UserChoice folder

If the first method does not help, we recommend that you carry out this second method.

Open the Windows 10 Registry Editor

Once here go to the following route:

EquipoHKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerFileExts

Expand the folder FileExts from the menu on the left side of the window. Here you will see a list of folders with the file extensions.

You will have to expand each of them, one by one, check if there is a folder called UserChoice.

If you find it, you must delete it by right clicking on it and in the menu selecting the option Get rid of