Your Virtualized server (i.e. server is not stand-alone, but part of a virtual cluster as in VM-Ware) will have the same name in your domain as the original server.
This makes thing a bit easier.
Just shut down QC (stop the ''HP Application Lifecycle Management'' service) during the server ''virtualization'', make sure you have migrated ALL of the QC databases (for projects AND qcsiteadmin_db), including retaining DB user rights per QC install guide (best if you can ''clone'' the DB instance).
Then when you bring up QC again, it will look in the same DB location based on the SAME dbserver name.
Be careful, though, if using SQL-Server with SQL-Server Authentication (QC uses a ''td'' user), you will need to run a stored procedure against every migrated DB to 'fix'' the ''td'' user behavior:
EXEC sp_change_users_login 'Update_One', 'td', 'td'
If using SQL-Server wtih Windows-authentication, you need to make sure the windows user specified to run the ''HP Application Lifecycle Management'' service still has appropriate rights (per ALM install guide) in the migrated DB instance.
If you are using ORACLE, make sure each Schema's schema-user (user with same name as schema) has the SAME password and rights as was used in previous DB instance.