Internet Information Server in Windows Server 2003 will throw 404 errors when ASP.NET 2.0 is not installed but the server is configured for ASP.NET 2.x under Properties > ASP.NET > ASP.NET version in the IIS management console (MMC). Setting this value to ASP.NET 2.x will not install the ASP.NET Web Service Extension.
To install ASP.NET 2.x, open the Console to this location:
%systemRoot%\\Microsoft.NET\\Framework\\v2.0.50727\\
then run this command:
aspnet_regiis -i
This invokes the ASP.NET IIS Registration Tool. More information about this tool is here:
http://msdn2.microsoft.com/en-us/library/k6h9cz8h(VS.80).aspx