Some modules of the Win32 namespace need to be installed via the CPAN. Some other are in the core activestate distribution (although they are not part of the Perl source ) and I assume that is why they do not show as "installed" modules with ppm :

The builtin functions are marked as [CORE] and the other ones as [EXT] in the following alphabetical listing. The Win32 module is not part of the Perl source distribution; it is distributed in the libwin32 bundle of Win32::* modules on CPAN. The module is already preinstalled in binary distributions like ActivePerl.