Unable to load dynamic library 'd:\php\extensions\php_ifx.dll' -> Can' find

My php.ini file in Winnt directory:

;;;;;;;;;;;;;;;;;;;;;;;;;
; Paths and Directories ;
;;;;;;;;;;;;;;;;;;;;;;;;;
include_path	=  ; UNIX: "/path1:/path2"  Windows: "\path1;\path2"
doc_root		= d:\Inetpub\wwwroot					; the root of the php pages, used only if nonempty
user_dir		=					; the directory under which php opens the script using /~username, used only if nonempty
extension_dir	=d:\php\extensions\	; directory in which the loadable extensions (modules) reside
enable_dl		= On				; Whether or not to enable the dl() function.
									; The dl() function does NOT properly work in multithreaded
									; servers, such as IIS or Zeus, and is automatically disabled
									; on them.

I don't understand it ?!?!?.

Please help!!