Where are Windows DLLs???????

I consider myself a smart person. However, I can not seem to figure out where all the extension .dlls are located. The php.ini file that comes with PHP4 lists all of these extensions below. So where are they, and how can I get them?? There is nothing in the README file about this. Do I need them at all? Is support for some of them built into the Win32 binary? If so, why are the extensions listed in the php.ini? If not, where are the DLLs? The documentation is VERY poor regarding the PHP4 extensions!!!!! ;Windows Extensions ;extension=php_mysql.dll ;extension=php_nsmail.dll ;extension=php_calendar.dll ;extension=php_dbase.dll ;extension=php_filepro.dll ;extension=php_gd.dll ;extension=php_dbm.dll ;extension=php_mssql.dll ;extension=php_zlib.dll ;extension=php_filepro.dll ;extension=php_imap4r2.dll ;extension=php_ldap.dll ;extension=php_crypt.dll ;extension=php_msql2.dll ;extension=php_odbc.dll -zb