Hi virtualdive,
thank you very much for your answer! I have just installed all components of vSphere 5.5 on the physical machine and I have created a remote DB on SQL.
Now, based on your answer, I must uninstall only vCenter e reinstall it after have imported the 5.0 DB. SSO, Inventory Service and Web Client I think are OK and must not uninstalled. It's correct?
Thank you for your patience.
Matrix