ASP.Net with IIS 6.0

When ASP.NET is enabled on a server running Windows Server 2003, the ASP.NET request processing model depends on the application isolation mode in which IIS 6.0 is running. The preferred application isolation mode for IIS 6.0 is worker process isolation mode, which enables you to use application pools, worker process recycling, and application pool health monitoring. When IIS 6.0 is running in worker process isolation mode, ASP.NET uses the IIS 6.0 request processing model settings.

If you configure IIS 6.0 to run in IIS 5.0 isolation mode, ASP.NET runs in its own request processing model, Aspnet_wp.exe, and uses its own configuration settings for process configuration, which are stored in the Machine.config configuration file. When your server is running in IIS 5.0 isolation mode, the ASP.NET ISAPI extension implements a request processing model that is similar to worker process isolation mode and contains worker process management capabilities similar to those provided by the WWW service. ASP.NET also provides recycling, health monitoring, and processor affinity.

When ASP.NET is installed on servers running Windows XP or Windows 2000 Server, ASP.NET runs in IIS 5.1 or IIS 5.0, respectively, and runs in the Aspnet_wp.exe process by default. The ASP.NET request processing model provides process recycling, health detection, and support for affinities between worker processes and particular CPUs on a server with multiple CPUs.

When different versions of ASP.NET share the same application pool

"It is not possible to run different versions of ASP.NET in the same IIS process. Please use the IIS Administration Tool to reconfigure your server to run the application in a separate process."

This error occurs when more than one version of ASP.NET is configured to run in the same process. Different versions of the .NET Framework and run time cannot coexist side by side within the same process. Therefore, an ASP.NET application that uses one version of the run time must not share a process with an application that uses a different version. This error commonly occurs when two or more applications are mapped to different versions of ASP.NET but share the same application pool.