PHP/Apache/Windows 2000 - Does not send mail

Hi there, I installed PHP 4.0.6 on a Windows 2000 machine running Apache 1.3.22. I followed all the instructions for installation - added the php.ini file to the C:\winnt directory, added php to httpd.conf. I tried both the module and the CGI versions and the following problem still persisted: Whenever I try to use the mail() function to send a an e-mail with a single file attachment, I receive a server error. If I set the SMTP variable in php.ini to localhost (where I am running an SMTP server) , I receive a PHP error and Apache logs a 'Premature end of script headers: C:/php/php.exe' error. If my SMTP variable is set to either a remote host, php reports in the next browser window of a server error at the line containing the mail() function call. Do I have a permissions issue with any of my files or directories? I did not know how to set the IUSR_MachineName permissions as described in the instructions. Do I need to create such a user? where do I find it if it exists? Thanks for any response, Yuval