Today I performed the upgrade from VMware vCenter 4.0 to vCenter 4.1. My old vCenter server runs Microsoft Windows Server 2003 32-bits, since vCenter 4.1 is not supported on a 32-bit operating system I made a new 2008R2 VM on which I will install the new version.
First make a back-up of the VMware vCenter database, the datamigration utility will upgrade the database. After the upgrade it isn’t possible to start the vCenter 4.0 service anymore!
For the migration I’ve used the datamigration utility which is available on the vCenter 4.1. media kit. Everything worked strait forward except the backup of the vCenter database (MS SQL Express 2005). I think the problem occurs because in the past this instance is upgraded from MSDE 2000 to SQL Express 2005. After I changed the named pipe string in the SQL connection manager from \.pipeMSSQL$SQLEXPRESSsqlquery to \.pipesqlquery (VMware KB 1024490) and restarted the SQL service it worked fine.
See VMware KB 1021635 for datamigration instructions. This instruction is also availible as VMware KB Video;