"This installation package is not supported by this processor type." when installing vCenter 4.1

You are trying to install/upgrade vCenter 4.1 on a 32 bit host.

vCenter 4.1 only supports 64 bit Windows architectures and will no longer install on a 32 bit host.

You will need to migrate your vCenter Server to a 64 bit OS. Please see the following tutorial:  Using the Data Migration tool to upgrade VMware vCenter Server 4.1