Working on getting real high performance with nginx under windows I am rewriting code and already got around the fd_setsize issue following http://stackoverflow.com/questions/7976388/increasing-limit-of-fd-setsize-and-select/18530636
which is documented as http://support.microsoft.com/kb/111855

I came across an interesting issue (FD_SETSIZE compiled for 8196), when worker_connections is set to 1024 I can get a max of 4500 true concurrent connections working, when worker_connections is set to 2048 I can get a max of 9000 true concurrent connections working, is there some kind of recycling of FD going on inside nginx ? if not I need to look somewhere else.
I intend to also solve the worker_processes issue but I first want to find out who is recycling the FD's.