' this code assumes that you have used this Imports statement' Imports Microsoft.Win32Function IsExcelInstalled() As Boolean    ' Define the RegistryKey objects for the registry hives.    Dim regClasses As RegistryKey = Registry.ClassesRoot    ' Check whether Microsoft Excel is installed on this computer,    ' by searching the HKEY_CLASSES_ROOTExcel.Application key.    Dim regExcel As RegistryKey = regClasses.OpenSubKey("Excel.Application")    If regExcel Is Nothing Then        IsExcelInstalled = False    Else        IsExcelInstalled = True    End If    ' Always close Registry keys after using them.    regExcel.Close()End Function' ExampleIf IsExcelInstalled() Then    Console.WriteLine("Microsoft Excel is installed")Else    Console.WriteLine("Microsoft Excel is not installed")End If