I ran into this same problem on Server 2008, completely out of the blue. Tried the same steps as you also, with no luck. I ended up dumping the Winsock and Winsock2 settings from the registry from another (working) box and using those.
Download from here and here.
If you want to give it a shot, just back up HKLM\SYSTEM\CurrentControlSet\Services\WinSock and HKLM\SYSTEM\CurrentControlSet\Services\WinSock2 first to be safe. After you back those keys up, delete them from the registry, then import and reboot. Dumped from Server 2008 x86.
Update: The original question was for Windows Server 2008, but the solution is easier for Windows Server 2008 R2 and Windows Server 2012 (and Windows 7 and 8). You can add the user through the NTFS UI by typing it in directly. The name is in the format of IIS APPPOOL\{app pool name}. For example: IIS APPPOOL\DefaultAppPool.
IIS APPPOOL\{app pool name}
Note: Per comments below, there are two things to be aware of:
- Enter the string directly into the "Select User or Group" and not in the search field.
- In a domain environment you need to set the Location to your local computer first.
Reference to Microsoft Docs article: Application Pool Identities > Securing Resources
Original response: (for Windows Server 2008) This is a great feature, but as you mentioned it's not fully implemented yet. You can add the app pool identity from the command prompt with something like icacls, then you can manage it from the GUI. For example, run something like this from the command prompt:
icacls c:\inetpub\wwwroot /grant "IIS APPPOOL\DefaultAppPool":(OI)(CI)(RX)
Then, in Windows Explorer, go to the wwwroot folder and edit the security permissions. You will see what looks like a group (the group icon) called DefaultAppPool. You can now edit the permissions.
However, you don't need to use this at all. It's a bonus that you can use if you want. You can use the old way of creating a custom user per app pool and assigning the custom user to disk. That has full UI support.
This SID injection method is nice because it allows you to use a single user but fully isolate each site from each other without having to create unique users for each app pool. Pretty impressive, and it will be even better with UI support.
Note: If you are unable to find the application pool user, check to see if the Windows service called Application Host Helper Service is running. It's the service that maps application pool users to Windows accounts.
Best Answer
I would count it as a bug but there might be some debate - what's happening is that the NLB configuration process requires elevation at some stage but fails to do so in a way that triggers the elevation prompt. With UAC enabled if you use the built in Administrator account or if the systems are part of a domain then a Domain Administrator account automatic elevation gets triggered. Accounts that are "merely" members of the local Administrators group do not behave this way and this results in a number of problems like this (e.g. you cannot connect to a remote admin share on a W2K8 system with an account unless it is The local Administrator or a member of Domain Administrators).
This behavior can be changed by GPO - there are some details in this technet article (it's about Vista but it applies to W2K8 servers in domain too).