In Utopia, this information would be baked into the installer. But since we don't live there, here goes:
1. create new database dotnetnuke in sql 2008
2. under security>logins>new login, add "NT AUTHORITY\NETWORK SERVICE"
3. security>logins>NT AUTHORITY\NETWORK SERVICE, right-click Properties, under User Mapping, check dotnetnuke, db_owner
4. in IIS Admin>Content View>Application Pools>dotnetnuke, right-click>Advanced settings>Identity = NetworkService
5. run web platform installer for community edition from the download link
Would appreciate if someone could update this for running under the appPool account. I tried and failed.