As someone who has just setup an almost identical Moodle server to what you are suggesting I would strongly suggest you consider some changes....
First Windows 2003, Apache and PHP were NOT a real stable solution for us and we tried HARD to fix it to work.
If you do a Google search on " memory leak with Apache 2.x /PHP 5.x and Windows 2003 server" you will find hundreds of complaints going back to 2002, of a serious memory leak that seems to never have been resolved.
It appears that PHP scripts and Apache under Windows 2003 lets PHP script requests use memory but never release it.
We tried at least 6 combinations of Apache 2.0, 2.0.55, etc and at least three versions of PHP 5.0 5.1, 5.24 and all we did for a month was watch the Moodle Apache Child process (either Apache.exe or Httpd.exe) eat memory up to 4 or 500 MB then crash and stop responding. We had to watch this happen hourly and the only "solution" was to limit MaxReqThreads per child so the Apache server would be forced to restart itself silently 2-3 times a day. ugly, very ugly...
Do yourself a favor and either use IIS for the webserver, or try linux. We are going back to linux. Our last Debian Moodle server ran for 3.5 years w/o a reboot.
The Windows Moodle box needed daily rebooting with Apache and ran at about 1/4 as fast as the Linux box did.
We needed apache because we needed virtual hosts, (not easy to do with IIS) if you don't need virtual hosts then IIS may be more stable, but just let me say our experience was horrible, and I am never going to try windows 2003, Apache and PHP together again. We contacted sites all over the world for advice and NO ONE seemed to have solved the memory leak issue without the ugly "hack" of a nightly or daily reboot of Apache which did reclaim the lost memory. Good luck and if you hear from someone who got a working combination of PHP, Apache, and Win 2003 be sure to find out EXACTLY what version they used. One solution suggested was to use "Fastcgi" in place of some of the classic PHP options but we didn't try that.
Good luck, and my suggestion would be to find a second server box to setup Linux on just in case you hit the problems we did.