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Find the registry key for the application you wish to associate, lets say for Notepad++.exe in HKEY_CLASSES_ROOTApplicationsnotepad++.exe shellopencommand

Check if the .exe path is right. If not, then change the path to the correct one.

After doing this, you can now go to the file you wish to associate and use the standard way Open With and choose the program you wish to open.

Explanation:

This issue happens when Windows gets confused about the filepath for a program, as file associations are handled using only the base executable name of a program (source).

This bug can be caused by:

• Running multiple versions of a program (i.e. Notepad++ and Notepad++ Portable)


• Moving programs to different folders.


• Changing drive letters

I had the same problem, and none of the solutions worked (like the method below of going to the Control Panel - which does the same thing if you right click the file->Open With->Choose Default). Even after selecting the new program many times, it was stuck with the old one.

I fixed it by editing the registry. Go to the concerned extension like this (I had problem with .cpp):

HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerFileExts.cpp

Besides these two keys: OpenWithList and OpenWithProgids, it might have a third one called 'UserChoice'. Just delete that third key. After that, it will allow you to change the default program for that file extension.

example : file type .css

find and delete key

HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerFileExts.css



HKEY_CURRENT_USERSoftwareMicrosoftWindowsRoamingOpenWithFileExts.css



HKEY_CLASSES_ROOT.css

open task Manager and Restart Windows Explorer Or reboot computer

Try

Control PanelAll Control Panel ItemsDefault ProgramsSet Associations

ADDED

Also see the question here ftype changes are ignored. Where does Windows retrieve the "incorrect" value from? How can I enforce my changes? for an example of the assoc and ftype commands. Starting an administrative cmd prompt and running the assoc command for the extension, then the ftype command for it, should associate the extension with the program you specify.

I wanted to share my solution. I wanted to open .spq with SpeQ Mathematics.exe, which is a standalone program (it does not require installation). The program did not appear in the list even after I found it via browsing and selected it.

I went to

HKEY_CLASSES_ROOT.spq

and found listed Data: spq_auto_file

I then went to

HKEY_CURRENT_USERSoftwareClassesspq_auto_fileshellopencommand

and saw the wrong folder listed under Data.
I changed the folder to the actual one and the program appeared in the context menu list. I suppose the moving around that can be done with standalone programs was the reason for my problem.

I was able to fix my problem with the program itself. See the picture below for reference; under 'Tools' > 'Options'

The 'Miscellaneous' tab; under 'Registry Setup' there are two options that alter the registry. I applied both and it works now. What isn't clear is how I could have done this without the program doing this.

I've had the same/similar problem.

Here is what caused it. I use keepass.exe to open .kbd files both of which I synch over cloud. When I moved the folder it stopped working. The OS knows that that's my program, but I'm unable to update the location of the executable through the Open-with dialog.

The solution...

• Open regedit


• find the application you are looking for in HKEY_CLASSES_ROOTApplications.
  
  
  
  
  • Example: atom.exe is located at HKEY_CLASSES_ROOTApplicationsatom.exe
  
  
  
  


• delete that entry


• right-click the file type and try selecting the program again. It should now appear

Just for you guys to know...

I had the same problem on win8.1.

That default file dialog seems to hang explorer, it happens both from the folder´s right click option and from set association screen, I think there is some problem with that functionality...

For me, killing explorer process via Task Manager and reopening explorer, (from task manager) via File -> new Task -> explorer.exe, completed the process of setting the default program normally and everything works fine now.

I don´t know if was just luck, but it is worth trying...

For anyone having the same issue but with Office 365 / Excel 2016:

Going to "Programs and Features" -> right click "Office 365" -> change -> Quick Repair fixed the issue for me.

You can use this command for ".txt" files. but you must open command prompt with admin roles.
ftype txtfile="C:Program Files (x86)Notepad++notepad++.exe""%1"

if you don't know file type of your file you can use "assoc .txt" command on command prompt.

For more details you can check this link:
Windows “Open With” application not appearing as an option

It works for me.

i fixed this issue by right-clicking the file i wanted to open and choosing "properties". on the "general" tab it said "opens with: unknown program" or something like that. i just clicked the "change..." button next to that message and picked the app i origionally wanted. i think maybe this happens when the associated application gets deleted.

The best solution is to remove the user account that cannot set a default program to open a file and re-create a new user. At some point when installing/updating an application, Windows corrupted the policy for that user account. Be sure to copy all the user's data (c:/users/userid/) before removing that user account and log in with a different user with Sysadmin account.

To Remove the user account: Control Panel >> System >> Advanced system settings >> Advanced (tab) >> Setting (under User Profile) >> delete the corrupt user account.

Then reboot, log in and create a new user. You can use the same account name.

Try setting the default from within the program you want to use as opener.

I had similar problem when php files all of a sudden started opening with Acrobat which caused an error as Acrobat can't handle php. I tried to change the association, but all failed. Finally went to Dreamweaver's preferences and set it as opener for php.