In IIS 5.6, the worker process being used was aspnet_wp.exe while in IIS 6.0, the worker process being used in w3wp.exe

On Windows 2003 (IIS 6.0) running in native mode, the component is running within the w3wp.exe process associated with the application pool which has been configured for the web application containing the component.
On Windows 2003 in IIS 5.0 emulation mode, 2000, or XP, it’s running within the IIS helper process whose name I do not remember, it being quite a while since I last used IIS 5.0.