reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.mht\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.MHT /f
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.html\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.HTM /f
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.htm\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.HTM /f
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.url\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.URL /f
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.mhtml\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.MHT /f
reg add HKCU\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\https\UserChoice /v Progid /t REG_SZ /d IE.HTTPS /f
reg add HKCU\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\ftp\UserChoice /v Progid /t REG_SZ /d IE.FTP /f
reg add HKCU\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\http\UserChoice /v Progid /t REG_SZ /d IE.HTTP /f
reg add HKCU\Software\Clients\StartMenuInternet /t REG_SZ /d iexplore.exe /f
reg add HKCU\Software\Microsoft\Windows\Shell\Associations\MIMEAssociations\message/rfc822\UserChoice /v Progid /t REG_SZ /d IE.message/rfc822 /f
reg add HKCU\Software\Microsoft\Windows\Shell\Associations\MIMEAssociations\text/html\UserChoice /v Progid /t REG_SZ /d IE.text/html /f
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.xht\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.XHT /f
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.xhtml\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.XHT /f
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.svg\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.SVG /f
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.partial\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.PARTIAL /f
reg add HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.website\UserChoice /v Progid /t REG_SZ /d IE.AssocFile.WEBSITE /f
Otra forma de hacerlo es por GPO/GPP, adjunto una captura de como quedan las entradas configuradas:
Action : ReplaceHive : HKEY_CURRENT_USERKey Path: Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.mhtValue name: UserChoiceValue type : REG_SZValue data : IE.AssocFile.MHT
Y por ultimo creando un script, como se describe en el siguiente enlace http://technet.microsoft.com/en-us/library/cc758918%28v=WS.10%29.aspx
Espero que os sirva de ayuda! Un saludo.