Problems opening file + str_replace

Hi! Let me describe my problem: I have this form where I browse for files (powerpoints) on my computer. I select a file, click the open-button and I go to another page that is supposed to open my powerpoint-file (in_pp2.php). The thing is that I need to str_replace some parts of the filename. It usually comes out lookin like this file///D://my_powerpoint.ppt but needs to be D:/my_powerpoint.ppt, in order for me to open it. Therefore I have a str_replace that should take care of the problem, but it still won't work for some reason. I have tested the str_replace function when I manually set $path = file:///D://my_powerpoint.php, and then it does the correct replacing. But why won't it replace the characters when I'm sending the path through this form Any ideas, help would be greatly appreciated, since this problem has been bugging me for two days now. Thanks! in_pp.php <? require("dbmanager.php"); ?> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>Browse powerpoint</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link href="style2.css" rel="STYLESHEET" type="text/css"> </head> <body> <form name="sendFile" method="post" action="in_pp2.php" enctype="multipart/form-data"> <input type="hidden" name="path"/> <input type="hidden" name="isubmit" value="Open"/> <input type="file" size="15" name="file" class="button"/> <input type="button" value="Open" class="button" OnClick="this.form.path.value = this.form.file.value; this.form.submit()"> </form> </body> </html> in_pp2.php <?php $path= $_POST["path"]; $path = str_replace("file:///","", $path); $path = str_replace("://",":/", $path); header("Location: $path"); exit; ?>