Opening a specific folder from VB

Hi

I am trying to open a specified folder location from VB

I am using Process.Start("C:\temp") as example and this works fine

But some of the paths I want to open won't work in same way

e.g. Process.Start("%WINDIR%\Installer")

gives "System.ComponentModel.Win32Exception: 'The system cannot find the file specified'"

Some other forum mentioned doing it like this Process.Start("explorer.exe", "%WINDIR%\Installer") but that just opens my Documents folder instead of specified path

It seems to be paths that have environment variables in e.g. %WINDIR% or %APPDATA% etc

Any thoughts please