Verifica che nel registro in HKCR\.scf\(Predefinito) ci sia come valore "SHCmdFile" e che sotto HKCR\SHCmdFile ci sia una struttura di questo genere:
codice:
[HKEY_CLASSES_ROOT\SHCmdFile]
"NeverShowExt"=""
@="Windows Explorer Command"
"InfoTip"="prop:DocComments"

[HKEY_CLASSES_ROOT\SHCmdFile\CLSID]
@="{57651662-CE3E-11D0-8D77-00C04FC99D61}"

[HKEY_CLASSES_ROOT\SHCmdFile\shell]

[HKEY_CLASSES_ROOT\SHCmdFile\shell\open]

[HKEY_CLASSES_ROOT\SHCmdFile\shell\open\command]
@="explorer.exe"

[HKEY_CLASSES_ROOT\SHCmdFile\shell\open\ddeexec]
@="[ShellFile(\"%1\",\"%1\",%S)]"
"NoActivateHandler"=""

[HKEY_CLASSES_ROOT\SHCmdFile\shell\open\ddeexec\Application]
@="Folders"

[HKEY_CLASSES_ROOT\SHCmdFile\shell\open\ddeexec\Topic]
@="AppProperties"

[HKEY_CLASSES_ROOT\SHCmdFile\shellex]

[HKEY_CLASSES_ROOT\SHCmdFile\shellex\DropHandler]
@="{86C86720-42A0-1069-A2E8-08002B30309D}"

[HKEY_CLASSES_ROOT\SHCmdFile\shellex\IconHandler]
@="{57651662-CE3E-11D0-8D77-00C04FC99D61}"
(@ qui rappresenta il valore "(Predefinito)").