How to change the account which SSRS Report Manager Web application runs under

After changing the selected account in both application pool and the rsreportserver.config file, you must force IIS to use NTLM as your authentication mechanism if you want to use Integrated Windows authentication only. To do this, follow these steps on the server that is running IIS:

1. Start a command prompt. 
2. Locate and then change to the directory that contains the Adsutil.vbs file. By default, this directory is C:\Inetpub\Adminscripts.
3. Type the following command, and then press ENTER:

cscript adsutil.vbs set w3svc/NTAuthenticationProviders "NTLM"

4. To verify that the NtAuthenticationProviders metabase property is set to NTLM, type the following command, and then press ENTER:

cscript adsutil.vbs get w3svc/NTAuthenticationProvider

The following text should be returned:

NTAuthenticationProviders       : (STRING) "NTLM"