64-bit ASP.NET is registered. Require 32-bit ASP.NET to install Microsoft Reporting Services 2005(32-bit).

On Windows Server 2003 64-bit edition, when installing Microsoft SQL Server 2005, ASP.NET Version Registration Requirement has a warning that says:
64-bit ASP.NET is Registered. Required 32-bit ASP.NET to install Microsoft Reporting Services 2005(32-bit).

To resolve this, simply switch the registered ASP.NET version to the 32-bit version by doing the following:

1. First, uninstall the 64-bit version: c:\WINDOWS\Microsoft.NET\Framework64\v2.0.50727\aspnet_regiis.exe -u

2. Configure IIS to run in WOW64 mode:

cscript.exe C:\inetpub\adminscripts\adsutil.vbs SET W3SVC/AppPools/Enable32bitAppOnWin64 1

3. Lastly, install the 32-bit version:

c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\aspnet_regiis.exe -i