Just upgrade to PHP 4.3.1. All the required libraries are included with the distribution (you better use the manual setup, not the php installer). Follow the setup instructions, which are partly a bit chaotic, but should get you done within about five minutes.

Note: If you use your old php.ini, make sure, you quote out the php_ctype.dll, since it seems, to be built in since 4.3 (had several errors "redefinition of <function-name>" occuring when [re]starting apache).
En clair assure-toi d'avoir décommenté la ligne de l'extension php_ctype.dll dans ton php.ini :
;PHPExt
extension=php_ctype.dll


If any libraries can not be found again, make sure the php4ts.dll resides in the same directory as php.exe or the php4<yourserver>.dll. Alse be sure to use php4apache2.dll, if you are running Apache Version 2.x. Also (lib)expat.dll and the rest of the above mentioned files should be able to be found (reside in a directory, that can be accessed through the path). I just checked and tested removing all files I moved to the system32 directory. You just need the files "expat.dll" and "sablot.dll" there. I removed "xmltok.dll", "xmlparse.dll" and "iconv.dll" again, and it still works fine.