Vista - Can you unassociate a file with a program?

I accidentally opened a file with windows and cannot remove the file
association. I don't wish to change it just remove it.

If you mean that you want to delete the file extension type reference completely off your computer, then:
1. Open regedit (type in Start Search area of Start Menu and press Enter)
2. Open "HKEY_CLASSES_ROOT"
3. Find the file extension and right click it and click delete.
4. Answer Yes to the confirmation prompt.

If you want to remove the program associated with the file extension and leave it blank, then do the above except instead of step 3:
1. Find the file extension and right click on the "Default" in the right pane.
2. Click Modify and leave the entry blank and click Ok.


Let me know if this is not what you meant, and I'll try and help.

Hope this helps,
Shawn

It kinda depends on the extension you associated. If it's a .dll, or.exe,
or .sys, or .lnk, for example, then no, you don't want to change it (well,
you do, but to what? there are a number of Windows files that open with
Unknown Application, because of the nature of the file extension. Its
complexities may vary). If it's a file extension that windows doesn't use,
like one you made up, say, .xyz, then yes, you can remove it in the
registry.

If you are trying to change an extension back to it's original state,
associated with its original Unknown Application, you might
have to state which file extension it is, if you need directions as to how
to restore it.

"cturtle" <cturtle@discussions.microsoft.com> wrote in message
news:2798A01E-5BCF-4B2C-87BF-057E0F843539@microsoft.com...
>I accidentally opened a file with windows and cannot remove the file
> association. I don't wish to change it just remove it.

An utility to unassociate file types in Windows Vista:
http://www.winhelponline.com/articles/231/1/

--
Regards,

Ramesh Srinivasan, Microsoft MVP [Windows Shell/User]
Windows® Troubleshooting http://www.winhelponline.com


"cturtle" <cturtle@xxxxxx> wrote in message news:2798A01E-5BCF-4B2C-87BF-057E0F843539@xxxxxx
I accidentally opened a file with windows and cannot remove the file
association. I don't wish to change it just remove it.

1. Click the Start Orb
2. In the Search Box, type "Default Programs" (without the quotes) and then open it
3. Click on Associate a file type or protocol with a program. It will take a few seconds for Windows to initialize the list.

This will allow you to change associations, but there doesn't seem to be a way to completely remove a file association. You may have to resort to editing the registry, as other posters mentioned.