Problemas com IIS - Service Unavailable

Segue alguns links para solução deste problema:

Assign NTFS Permissions

http://msdn.microsoft.com/en-us/library/Aa508562#secmod15_assignntfspermissions

How To Create a Custom Account to Run ASP.NET

http://msdn.microsoft.com/en-us/library/Aa508562#secmod15_assignntfspermissions

Failed to execute request because the App-Domain could not be created. Error: 0x80070005 Access is denied.

http://forums.asp.net/t/960370.aspx