On the Box:
Server: windows 2008 server R2.
When installing Reporting Extensions for Ax 2009,the pre-requisite page shows that IIS is not installed even thou you may have installed it. In the log file,you will find that the installation fails at IIS.
For the workaround, install the following IIS components from Manage Your server-> Server Roles->role services.
Install the selected components and You wont be asked to install IIS pre-requisite.