POSTing files to IIS

Hello! I try to realize an file-upload to IIS, but it seems impossible to me without help. I came so far, that I get all variables through, which were sent with the html-form, but I can't get even the $userfile, nor I know where a (possible?) temporary upload-dir could be (therefore, this setting in the php.ini isn't filled out). I have installed PHP 4 PL2 via ISAPI, and IIS 4. I'd highly appreciate any help in this manner! Many thanks in advance, Thomas