remove opens with proram on a given file type

[will]

I have a configuration file I want to change back to it's
original state... in the properties window where you'll
find Opens With it reads "Unknown Applicaion" I
accidentally clicked change and it changed to "WordPad". I
need to change this back and I don't know how.... Please
Help!!!!

 

[Ndi]

If it didn't open with anything before, easiest way is to go to Tools menu
in Explorer and choose Options.

Go to File Types and type CFG (to get to "configuration file", or whatever
the extension is). Then, after selecting it, choose "delete" to delete the
association. This will revert it to "unknown".

To get more advanced repair, open Regedit and perform the following steps:

+ Get to HKEY_CLASSES_ROOT
+ Locate .cfg key (folder) under
+ Open it and read the default value(file). It should read "cfgfile" or
similar.
+ Go to the cfgfile key (folder) in HKEY_CLASSES_ROOT (HKCR\cfgFile)
+ There is a DefaultIcon key. Delete it.
+ It has a Shell key. If this has a default value, delete it.
+ The Shell has one or more subkeys, one of them will probably be "Open".
Delete those keys.

After logging on and off (to be sure, you can also wait), the cfg files
should lose thir new Notepad icon and double-clicking it should not bring up
Notepad.

Note that this will present problems under XP.