Installing and upgrading help

I have an installation of Moodle 1.4.2+ working fine on a Windows 2000 box, and am trying to migrate to a Windows 2003 server. I simply cannot get Moodle 1.4.2+ to recognize my working files directory.

I'm using Windows 2003, IIS 6 (running PHP 4.8.3 as an ISAPI in IIS 5 emulation mode--it's the only way I can get PHP to work with MySQL). My working files folder sits outside of the Moodle installation and has IUSR_[systemname] with read/write/modify permissions. I even tried giving "Everyone" full control over the folder. No matter what I do, though, Moodle tells me that it can't find the working directory. The path is typed correctly into the config.php file; there are no typos.

It'll work if I put the working files folder inside of the Moodle folder, but that's an unacceptable solution, security-wise. (It'll work ... sort of. I can't log in as admin or any user. I just get bumped back to the welcome page without being logged in. But that's another thread for another day.)

Am I not setting the permissions correctly in IIS 6 / Windows 2003 for this folder? Should I try a more recent build of Moodle?

Thanks in advance for any help ...