Vivenciei um problema semelhante há muito tempo e acabei resolvendo essa bagunça.
Há uma correção de correção de contorno (desenvolvida por Ramesh Srinivasan) que evita essa redefinição súbita de associações de arquivos no Windows 10.
Since the culprits are windows 10 modern apps this fix works to
prevent Windows 10 from resetting the file associations by setting
NoOpenWith registry value for all the modern apps.
Aqui está o restante do conteúdo do arquivo .reg:
Windows Registry Editor Version 5.00
;-------------------
;Microsoft.3DBuilder
;-------------------
;File Types: .stl, .3mf, .obj, .wrl, .ply, .fbx, .3ds, .dae, .dxf, .bmp
;... .jpg, .png, .tga
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXvhc4p7vz4b485xfp46hhk3fq3grkdgjg]
"NoOpenWith"=""
;-------------------
;Microsoft Edge
;-------------------
;File Types: .htm, .html
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppX4hxtad77fbk3jkkeerkrm0ze94wjf3s9]
"NoOpenWith"=""
;File Types: .pdf
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXd4nrz8ff68srnhf9t5a8sbjyar1cr723]
"NoOpenWith"=""
;File Types: .svg
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXde74bfzw9j31bzhcvsrxsyjnhhbq66cs]
"NoOpenWith"=""
;File Types: .xml
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXcc58vyzkbjbs4ky0mxrmxf8278rk9b3t]
"NoOpenWith"=""
;-------------------
;Microsoft Photos
;-------------------
;File Types: .3g2,.3gp, .3gp2, .3gpp, .asf, .avi, .m2t, .m2ts, .m4v, .mkv
;... .mov, .mp4, mp4v, .mts, .tif, .tiff, .wmv
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXk0g4vb8gvt7b93tg50ybcy892pge6jmt]
"NoOpenWith"=""
;File Types: Most Image File Types
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppX43hnxtbyyps62jhe9sqpdzxn1790zetc]
"NoOpenWith"=""
;File Types: .raw, .rwl, .rw2 and others
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppX9rkaq77s0jzh1tyccadx9ghba15r6t3h]
"NoOpenWith"=""
;-------------------
; Zune Music
;-------------------
;File Types: .aac, .adt, .adts ,.amr, .flac, .m3u, .m4a, .m4r, .mp3, .mpa
;.. .wav, .wma, .wpl, .zpl
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXqj98qxeaynz6dv4459ayz6bnqxbyaqcs]
"NoOpenWith"=""
;-------------------
; Zune Video
;-------------------
;File Types: .3g2,.3gp, .3gpp, .avi, .divx, .m2t, .m2ts, .m4v, .mkv, .mod
;... .mov, .mp4, mp4v, .mpe, .mpeg, .mpg, .mpv2, .mts, .tod, .ts
;... .tts, .wm, .wmv, .xvid
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppX6eg8h5sxqq90pv53845wmnbewywdqq5h]
"NoOpenWith"=""
Após fazer alterações no registro, você pode mudar para o seu programa preferido e selecionar asscoiations de arquivo padrão. (Você pode precisar reiniciar)
Você pode desfazer essa alteração a qualquer momento, substituindo o valor de NoOpenWith:
Windows Registry Editor Version 5.00
;-------------------
;Microsoft.3DBuilder
;-------------------
;File Types: .stl, .3mf, .obj, .wrl, .ply, .fbx, .3ds, .dae, .dxf, .bmp
;... .jpg, .png, .tga
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXvhc4p7vz4b485xfp46hhk3fq3grkdgjg]
"NoOpenWith"=-
;-------------------
;Microsoft Edge
;-------------------
;File Types: .htm, .html
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppX4hxtad77fbk3jkkeerkrm0ze94wjf3s9]
"NoOpenWith"=-
;File Types: .pdf
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXd4nrz8ff68srnhf9t5a8sbjyar1cr723]
"NoOpenWith"=-
;File Types: .svg
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXde74bfzw9j31bzhcvsrxsyjnhhbq66cs]
"NoOpenWith"=-
;File Types: .xml
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXcc58vyzkbjbs4ky0mxrmxf8278rk9b3t]
"NoOpenWith"=-
;-------------------
;Microsoft Photos
;-------------------
;File Types: .3g2,.3gp, .3gp2, .3gpp, .asf, .avi, .m2t, .m2ts, .m4v, .mkv
;... .mov, .mp4, mp4v, .mts, .tif, .tiff, .wmv
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXk0g4vb8gvt7b93tg50ybcy892pge6jmt]
"NoOpenWith"=-
;File Types: Most Image File Types
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppX43hnxtbyyps62jhe9sqpdzxn1790zetc]
"NoOpenWith"=-
;File Types: .raw, .rwl, .rw2 and others
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppX9rkaq77s0jzh1tyccadx9ghba15r6t3h]
"NoOpenWith"=-
;-------------------
; Zune Music
;-------------------
;File Types: .aac, .adt, .adts ,.amr, .flac, .m3u, .m4a, .m4r, .mp3, .mpa
;.. .wav, .wma, .wpl, .zpl
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppXqj98qxeaynz6dv4459ayz6bnqxbyaqcs]
"NoOpenWith"=-
;-------------------
; Zune Video
;-------------------
;File Types: .3g2,.3gp, .3gpp, .avi, .divx, .m2t, .m2ts, .m4v, .mkv, .mod
;... .mov, .mp4, mp4v, .mpe, .mpeg, .mpg, .mpv2, .mts, .tod, .ts
;... .tts, .wm, .wmv, .xvid
[HKEY_CURRENT_USER\SOFTWARE\Classes\AppX6eg8h5sxqq90pv53845wmnbewywdqq5h]
"NoOpenWith"=-
O autor gentilmente disponibilizou este script reg online em seu site: Correção para “An App O padrão foi Redefinir ”Windows 10 Redefinindo Associações de Arquivos (Correções do Registro) e todo o crédito é concedido a elas .