How do I change a file with the extension of .txt to .dll or Windows Shell extension?

I changed a file from a .truststore which opens with windows shell to a .txt. I need to change it back.
Leah WhitneyAsked:
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Will SzymkowskiSenior Solution ArchitectCommented:
I am assuming that you are talking about File Associated program. If so, use the following link below to change it back.

Leah WhitneyAuthor Commented:
This is on server 2008 r2. I have a file that should be opening with Windows Shell how to I re-associate it?
Will SzymkowskiSenior Solution ArchitectCommented:
Windows 7 and 2008R2 are built on the same kernel so it will be the same steps. also hold shift+right click the file and select Open With > choose default program > select powershell.

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Leah WhitneyAuthor Commented:
Windows Powershell is not showing up but its clearly installed. Also when I browse for it search can't pick it up.
Will SzymkowskiSenior Solution ArchitectCommented:
You can press the browse button and navigate to the default location which is below...

David Johnson, CD, MVPRetiredCommented:
windows powershell is located in
Leah WhitneyAuthor Commented:
Okay I was able to associate with powershell but I don't believe that is the same as Windows Shell. I have attached a screen shot of another file that I'd like the .truststore to be associated with.
Leah WhitneyAuthor Commented:
I don't believe the file was ever really associated. As long as the file can be manipulated, I think that is all that matters. Unless you have any insight on that statement I will consider this solved.
Change it to .bat

Not clear what your txt file has to judge whether the .bat is an appropriate extention to use.
Leah WhitneyAuthor Commented:
This was my solution;

Let .<ext> be the extension you want to deassociate.
With a registry editor (e.g. regedit.exe),
1. go to
remove the subtree .<ext>
2. go to
remove the subtree .<ext>
remove the subtree <ext>_auto_file

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Leah WhitneyAuthor Commented:
Because it worked.
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