VMware supports in-place upgrades on 64-bit systems from vCenter Server 4.0 to vCenter Server 4.1.

You can upgrade VirtualCenter 2.5 and vCenter Server 4.0 to vCenter Server 4.1 by installing vCenter Server 4.1 on a new machine and migrating the existing database. This upgrade method makes it possible to upgrade from a 32-bit system to a 64-bit system.

vCenter Server 4.1 can manage ESX 3.x/ESXi 3.5 hosts in the same cluster with ESX 4.x/ESXi 4.x hosts. ESX 2.x hosts cannot be managed by vCenter Server 4.1.