Can't upload files using PHP - php

Question

I'm new to PHP and I'm learning from Headfirst PHP and MySQL book.
I've made a HTML form so the user can upload a file (in this case an image file).
Here is the code:
<?php
define('GW_UPLOADPATH', 'guitar/images/');
if(isset($_POST['submit'])) {
$name = $_POST['name'];
$score = $_POST['score'];
$screenshot = $_FILES['screenshot']['name'];
if(!empty($name) && !empty($score) && !empty($screenshot)) {
$target = GW_UPLOADPATH . $screenshot;
if(move_uploaded_file($_FILES['screenshot']['tmp_name'], $target)) {
$dbc = mysqli_connect('localhost', 'root', '', 'guitar')
or die('Error connecting to MySQL server');
$query = "INSERT INTO guitarwars VALUES (0, '$name', '$score', NOW(), '$screenshot')";
$result = mysqli_query($dbc, $query) or die('Error querying database.');
echo '<p>Thanks for adding your new high score!</p>';
echo '<p><strong>Name:</strong> ' . $name . '<br />';
echo '<strong>Score:</strong> ' . $score . '</p>';
echo '<img src="' . GW_UPLOADPATH . $screenshot . '" alt="Score image" /></p>';
echo '<p><< Back to high scores</p>';
$name = "";
$score = "";
$screenshot = "";
mysqli_close($dbc);
}else{
echo '<p class="error">Sorry, there was a problem uploading your screen shot image.</p>';
}
}else{
echo '<p class="error">Please enter all of the information to add ' .
'your high score.</p>';
}
}
?>
When I put the index.php & images folder in the root folder of server everything is ok.
But when I create a directory (in this case: guitar folder) in htdocs folder (server root folder) and put project files in that directory the problem shows up.
Problem is that when user upload image file it does NOT go to images folder and this error shows up:
Warning: move_uploaded_file(guitar/images/jacobsscore.gif): failed to open stream: No such file or directory in C:\xampp\htdocs\guitar\addscore.php on line 35
Warning: move_uploaded_file(): Unable to move 'C:\xampp\tmp\phpE3BE.tmp' to 'guitar/images/jacobsscore.gif' in C:\xampp\htdocs\guitar\addscore.php on line 35