独特ですね。この const を宣言に追加し、OR値をオープン レジストリ呼び出しに追加してみてください。KEY_WOW64_32KEY および KEY_WOW64_64KEYへの回答には非常に良い説明があります。
Private Const KEY_WOW64_64KEY As Long = &H100& '32 bit app to access 64 bit hive
Private Function GetWindowsProductId() As String
Dim strReturn As String
Dim strBuffer As String
Dim lngType As Long
Dim lngBufLen As Long
Dim lngRst As Long
Dim hKeyHandle As Long
lngRst = RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SOFTWARE\Microsoft\Windows NT\CurrentVersion", 0, KEY_READ Or KEY_WOW64_64KEY, hKeyHandle)
If hKeyHandle <> 0 Then
strBuffer = String(255, vbNullChar)
lngBufLen = Len(strBuffer)
lngRst = RegQueryValueEx(hKeyHandle, "ProductId", ByVal 0&, lngType, ByVal strBuffer, lngBufLen)
If lngRst = 0 Then
If lngType = REG_SZ Then
If lngBufLen > 0 Then
strReturn = Left$(strBuffer, lngBufLen - 1)
Else
strReturn = "nothing was returned"
End If
Else
strReturn = "there was an error"
End If
ElseIf lngRst = 2 Then 'the key does not exist
strReturn = "the key was not found"
Else 'if the return is non-zero there was an error
strReturn = "There was an error " & CStr(lngRst) & " reading the key"
End If
End If
GetWindowsProductId = strReturn
End Function