I do have made an upload-function at a big website, but it runs on Debian Linux and therefore its a bit difficult for me to say what could be wrong.
But I'd start viewing the directory which you have specified in your php.ini-file. That way you can confirm if the file is uploaded or not.
As far as I know, PHP will attempt to remove the file when the script terminates, but then again (Windows) I don't know.
Third, it's always a good idea to use file_exists if you want to know if a file is uploaded.
Fourth, there's a few variables which is set when you upload a file :
$file - temporary filename in your tmp-folder
$file_type - mimetype of uploaded file - can be faked!
$file_size - size of the file uploaded
$file_name - original filename which can contain some "stupid" and unwanted chars!
I guess that's it - hope you manage to make it work.