server 2003, session ending questions

Is the worker process the same on a windows 2003 machine the same as it is on an XP pro machine? I was looking in the task manager for the aspnet_wp.exe, but couldn't find it. The real question is though, does anyone know reasons why sessions may be ending prematurely? I checked the timeout settings in machine.confing, in the iis application settings, and in web.config. All of the settings are at 1200 seconds or 20 minutes. The machine also hosts a few other servers and I thought that the worker process could be recycling itself for some reason. ANyone have any ideas on what to consider as the cause?"Application Pooling in IIS 6.0
IIS versions earlier than 6.0 use the ASP.NET process model (Aspnet_wp.exe). Under the ASP.NET process model, each unique application version automatically runs in a separate process at run time. All applications that target the same version of the runtime share the same process (or processes in Web garden mode). However, IIS 6.0 uses the IIS 6.0 process model (W3wp.exe) and introduces a new isolation feature called application pooling. Application pooling allows applications to run together in one or more processes, as long as they share the same pool designation. Applications that are assigned different application pools never run in the same process."
-- fromMSDN: Configuring an ASP.NET Application for an ASP.NET Version

If the wp is recycling, then you should find an error in the System Event Log (or possible Application Event Log).