I know this a not really an awnser to your question, but depending on what you are doing it may offer a solution.
Are you totally commited to using the Win32::API?
You can get the information you require using OLE as well, and it is much simpler.

use Win32::OLE;

$file = "M:\\poledit.exe";

$fso = Win32::OLE->new('Scripting.FileSystemObject') or die "Cannot op
+en File System Object";
$companyname = $fso->GetFileName ($file);
$version = $fso->GetFileVersion ($file);
print $companyname, "\t", $version;
[download]

Of course if you are looking to do more with the Win32:API then this doesn't really help you. :-)