In IIS7, my application pool is running under ApplicationPoolIdentity. How can I give this user file permissions when it doesn't show up as a User?
You can add the app pool identy from a command prompt like this:
icacls c:\inetpub\wwwroot /grant "IIS APPPOOL\DefaultAppPool":(OI)(CI)(RX)
Then, you can edit the security permissions through Windows Explorer.