Seems like it might be more effective to run an actual script to step through the process and diagnose where this is breaking down:

use strict;
use warnings 'all';

use Cwd;

my $docs = 'C:\Documents and Settings';

chdir($docs) || die "Couldn't change directory to $docs: $!";

print "Current directory is ", getcwd, "\n";

if (-r 'Administrator') {
        print "Administrator is readable.\n";
} else {
        die "Couldn't read 'Administrator': $!";
}

if (chdir('Administrator')) {
        print "Changed directory to Administrator.\n";
} else {
        die "Couldn't change directory to 'Administrator': $!";
}

print "Current directory is ", getcwd, "\n";

if (opendir(ADMINDIR, "$docs\\Administrator")) {
        print "Opened directory Administrator.\n";
} else {
        die "Couldn't open directory 'Administrator': $!";
}
[download]

By the way, be sure you're not trying to opendir on your directory after you've chdir'ed into it. I caught that mistake in whipping up the above. To opendir on your current working directory, you either have to opendir(DIR, '.') or provide the full path.