BES 4.0 is no longer supported by RIM. It's extremely old and its life ended a while ago.
If I may offer a better suggestion... install BES Express 5.0.2 (it's free) on your new Windows 2003 server and use the BlackBerry Enterprise Transporter to move your users over to the new BES.
All of the documentation for this type of migration is on RIM's website in the support section.