If PPM doesn't work, you can try this:

download the module's distibution from CPAN and unzip it in to a temp directory.

Copy any .pm files (and any subdirectories with .pm files) to the appropriate location under c:\perl\site\lib. e.g. the File::Backup distribution contains a file called Backup.pm which you can copy to c:\perl\site\lib\File\Backup.pm

Limitations: If the module depends on other modules, you will have to repeat the process for them. You'll have to build the HTML docs yourself - otherwise just use the docs on the web. Finally, this will only work for pure Perl modules.

I've had to resort to this many times - Parrot/Perl6 where art thou!