If i remember well the problem is that basically all extensions are enabled by default after the install if you do nothing, even theses needing proprietary dlls (like the pdo oracle one).
If you hand-pick the few extensions that you need most of the time it's either working directly or the dlls to use are pretty simple to find.
On my win7 x64 the following extensions are commented in my php.ini and i commented only the one that didn't want to load :
;extension=php_dbase.dll
;extension=php_fdf.dll
;extension=php_gmp.dll
;extension=php_interbase.dll
;extension=php_ldap.dll
;extension=php_ming.dll
;extension=php_oci8.dll
;extension=php_pdo_oci.dll
;extension=php_pdo_oci8.dll
;extension=php_pdo_sqlite.dll
;extension=php_pdo_sqlite_external.dll
;extension=php_pspell.dll
;extension=php_sqlite.dll
;extension=php_sybase_ct.dll
They are at the end of the file in lot of small ini sections.
Placing it in path is not necessary at all (and have never been necessary in fact, it's just easier now), a correct install could be done properly in Program Files as most software.
Or as you said in your comment you could use a version of php working with IIS directly pre-packaged like the one from microsoft. But i personally prefer to keep apache even on windows to be able to use mod_rewrite and .htaccess
files (as my final target is an apache install under linux)