64-bit Editions of IIS
IIS in SySWoW Mode
%1 is not a valid Win32 application
Re: %1 is not a valid Win32 application
Aug 15, 2008 08:46 PM|mukhtard|LINK
Are you trying to run the worker process as Wow64(32-bit)?
In that case there is a good chance that your configuration is trying to load some 64-bit isapi filter, for example aspnet_filter.dll,for v2.0, on a 64-bit OS there will be two instances of this dll on your machine under \framework and \framework64 folders.
You want to select the one under \framework.
IIS Performance Team