if ($os == 'Windows' && get_sub_field('windows')) {
// show a value
}
although I would probably use a switch statement
switch ($os) {
case 'windows':
$value = get_sub_field('windows');
break;
case 'Mac'
$value = get_sub_field('mac');
break;
// etc fro each os and field
}
if ($value) {
echo $value;
}