IIS uses MachineKeys for encryption. IIS 6.0 uses a particular key c2319c42033a5ca7f44e731bfd3fa2b5_GUID to do the encryption. If you have worked on IIS Admin start up issues the machine keys is one of the first things we check because if you do not have the proper machine key you cannot enumerate the metabase and hence the IIS Admin service will not be able to load the metabase.
On Windows 2003 the MachineKeys are located at
C:Documents and SettingsAll UsersApplication DataMicrosoftCryptoRSAMachineKeys
With Windows 2008 the user profiles are now stored in the Users folder and the MachineKeys are now under
C:UsersAll UsersApplication DataMicrosoftCryptoRSAMachineKeys
and the ones that concern IIS are