The answer is in this document on msdn:http://msdn.microsoft.com/library/d...1_2ard.asp
Setup error 25619
Setup uses IWAM_computername account to configure IIS. Disabling the account results in Setup error code 25619. This error will also occur if you are installing a report server on Windows XP and Distributed Transaction Coordinator service is not running. To work around this error, enable the account or start the service, and then rerun Setup.
I clipped out the section above, but I recommend you read the whole document.