can't figure out proper format for c:\ path for curl upload

I can't figure out how to pass a c:\... filepath via curl for an RFC1867 multipart form upload in PHP 5.2.1. I'm using the following code to perform a programmatic file upload to the PHP server: $filepath='/home/user/testfile.txt'; $ch=curl_init('http://bucksvsbytes.com/upload.php'); curl_setopt($ch,CURLOPT_POST,true); curl_setopt($ch,CURLOPT_RETURNTRANSFER,true); curl_setopt($ch,CURLOPT_POSTFIELDS,array('peru'=>'@'.$filepath)); curl_exec($ch); curl_close($ch); Works great if the file I want to upload is on the web server but it never is. The files I want are on the client computer, of course, e.g. c:\home\user\testfile.txt I've tried passing every variation of that path I can think of, e.g.: C:\home\user\testfile.txt C:\\home\\user\\testfile.txt C:/home/user/testfile.txt urlencode(...) utf8_encode(...) and nothing works. I either get the dreaded "failed creating formpost data" or the filepath shows up in $_POST and $_FILES is empty. The listed formats don't work with fopen() either. I've searched dozens of web examples but I can't get it. Help! For that matter, is there a better approach than curl for programmed uploads of client computer files to the PHP server?