I would normally run the CRM setup on the new IIS server, and select the option 'Connect to existing deployment' to use the current MSCRM_Config and organisation databases (assuming they are not being moved). Then uninstall CRM from the original server,
and remove the original server from the deployment using CRM Deployment Manager
If you also want to move the SQL databases, do this with SQL backup and restore, and do this before installing the new CRM server
For more information, see
http://support.microsoft.com/kb/952934/en-us
Microsoft CRM MVP - http://mscrmuk.blogspot.com/ http://www.excitation.co.uk