database does not have a valid owner

Error:
TITLE: Microsoft SQL Server Management Studio
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Database diagram support objects cannot be installed because this database does not have a valid owner. To continue, first use the Files page of the Database Properties dialog box or the ALTER AUTHORIZATION statement to set the database owner to a valid login, then add the database diagram support objects.
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BUTTONS:
OK
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Solution:
1. Right Click on your database, choose properties
2. Goto the Files
3. Change the owner textbox to "sa"
4. Press OK
5. Enjoy