I ran LibreOffice on a Win7x64 machine and did a manual association of .ODT files with it (the "Open with ..." operation). Then, when the LibreOffice folder moved, I couldn't re-set the file association.
Open regedit and delete the entire .odt key: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.odt
I had OpenOffice installed, opening ODT files by default. In an effort to fix a problem with OpenOffice quickly, I downloaded the "LibreOffice Still" Portable version to my Downloads folder
and set it as the default viewer. I later moved it to another folder
(where all my other portable applications are located) and just couldn't
fix the old association.
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