What do I need to do to install exchange 2003 on a new server while keeping the existing server up and running. I dont know what to do.

Hello, Its quite simple. Join new server into domain as a member server, after installing prerequisite for Exchange 2003 on it start installingExchange server.It will join into existing Exchange organization and both servers will start communicating.

In addition to what Amit stated, when you are ready to remove the first Exchange 2003 Server then follow this link, http://support.microsoft.com/kb/822931

Install additional exchange server 2003: Make sure the server meets the requirements for an Exchange 2003 server Make sure to join the existing Exchange 2003 Organization Adding second exchange to an existing organization is almost same as the first one. The only different in the Installation Wizard is, you will see two more dialog boxes when you have more than one AD or RG. The first dialog is to choose AG, second is for RG Still follow the article of Installing New Exchange 2003 Servers except to ForestPrep and DomainPrep