how to reset File type association?

[David ......M...........]

On my XP Home ed system somehow the .dat file type has
been associated with windows media player. All .dat files
have the wmp icon against them. If in windows explorer I
go tools > folder options > file types the .dat extension
is not listed.

How can I remove this association of .dat and wmp?

I recently installed Microsoft Plus! Digital Media
Edition I don't know if this is what caused this mismatch
of file extension association to wmp.

Many thanks

David

 

[Doug Knox MS-MVP]

By default, there are no associations for DAT files. Click Start, Run and
enter REGEDIT Go to:

HKEY_CLASSES_ROOT\.dat

Delete everything under the .dat sub-branch. Then right click in a blank
area of the right pane and select New, String value and name it NoOpen.
Leave the value empty.

If you wish, you can right click on the .dat sub-branch, right click and
select Export. This creates a backup REG file, just in case.

 

[David .....M.......]

Many thanks Doug,

That fixed it. There was a registry entry named perceived
type with a value of video under HKEY_CLASSES_ROOT\.dat
There was already a NoOpen key with no value so I just
deleted that perceived type key, rebooted and the wmp
icon is no longer associated with the .dat file type.

Many thanks, it was annoying me seeing the wmp icon
against .dat files!

David