Database owner and table owner are two different things.
Do you have the SA or Sysadmin account information? If so, just log in as that and you should have all the rights you need to do whatever you want.
If you're actually trying to change the owner of a user owned database/table/object, you can use the sp_changedbowner or sp_changeobjectowner system stored procedures.
Caveats are as follows:
To use sp_changeDBOwner, youneed to be Sysadmin or the current owner of the db.
To use sp_ChangeObjectOwner you need to be Sysadmin or be assigned to the DBO, db_ddladmin or db_securityAdmin roles.
Hope that helps.
Catadmin - MCDBA, MCSA
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