vCenter Server 5.5 does not support Windows Server 2003 as a host machine, and does not support upgrades from Windows Server 2003 hosts. You can install vCenter Server 5.5 and related components on a supported host and migrate configuration data from your existing Windows Server 2003 installation.
Procedure
Install vCenter Single Sign-On in a Migration to vSphere 5.5 from a Windows Server 2003 Host vCenter Server 5.5 does not support Windows Server 2003 hosts for vCenter Server. When you migrate from a Windows Server 2003 host to a host that is supported for vCenter Server 5.5, install vCenter Single Sign-On on the new host.
Install or Upgrade the vSphere Web Client The vSphere Web Client lets you connect to a vCenter Server system to manage your vSphere deployment through a browser.
Migrate vSphere Web Client Data from a Windows Server 2003 Host When you migrate from a Windows Server 2003 host to a host that is supported for the version 5.5 vCenter Server, you can also migrate some configuration data.
Migrate vCenter Inventory Service Data from a Windows Server 2003 Host When you migrate from a Windows Server 2003 host to a host that is supported for vCenter Single Sign-On 5.5, you can also migrate Inventory Service SSL certificates and configuration data.
Install Inventory Service in a vCenter Server Migration from a Windows Server 2003 Host After you migrate Inventory Service SSL certificates and configuration data from a Windows Server 2003 host to a host that is supported for Inventory Service 5.5, you can install Inventory Service on the new host.
Migrate vCenter Server Data from a Windows Server 2003 Host When you migrate from a Windows Server 2003 host to a host that is supported for vCenter Single Sign-On 5.5, you can also migrate the vCenter Server database and SSL certificates.
Install vCenter Server in a Migration from a Windows Server 2003 Host After you migrate vCenter Server SSL certificates from a Windows Server 2003 host to a host that is supported for vCenter Server 5.5, you can install vCenter Server on the new host.