Hardly can I find this. But, those required dll is not included in the package and no link for download.
It's a pitty that no discussion about this within php.net
Note to Win32 Users: In order to enable this module on a Windows environment, you must copy several files from the DLL folder of the PHP/Win32 binary package to the SYSTEM32 folder of your windows machine. (Ex: C:\WINNT\SYSTEM32 or C:\WINDOWS\SYSTEM32). For PHP <= 4.2.0 copy sablot.dll and expat.dll to your SYSTEM32 folder. For PHP >= 4.2.1 copy sablot.dll, expat.dll and iconv.dll to your SYSTEM32 folder.