See http://www.windowsitpro.com/article/services/understanding-the-local-service-and-network-service-accounts.aspx

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>What do you specify for account name and password for various services (when installing SQL Server 2008). The list of services is: SQL Server Agent, SQL Server Database Engine, SQL Server Analysis Services, etc. Is it a good idea to specify one/same account for all and have it as Windows Authentication?
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>TIA
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>UPDATE:. The question should be more specific (now that I read more about this). Which services should be set to Network Service and which are to Local Service or it does not really matter?