use warnings;
use strict;

#                      Folder                Readme
my %oses = ("170" => ["winvista",           "readme_winvista.txt"],
            "173" => ["winvista64",         "readme_winvista64.txt"],
            "119" => ["winvxp",             "readme_winxp.txt"],
            "210" => ["winxp64",            "readme_winxp64.txt"],
            "541" => ["windows*7 graphics", "readme_windows *7 graphic
+s .txt"],
            "525" => ["winvista64",         "windows *7 /windows *7/wi
+ndows *.txt"]);

my $os = '210';
my $Folder = "win2k_xp"; 
my $Readme = "readme_2k_xp.txt";

if (exists $oses{$os}) {
    $Folder = $oses{$os}[0];
    $Readme = $oses{$os}[1]
}

print "Folder: $Folder, Readme: $Readme\n";
[download]

Update: Added default handling.