I use windows 2003 on my main system and I'm sure there's alot of other people out there that have modified this OS as much as I have. Doom3 will NOT even install on this OS, so I thought I'd share what I had to do to make it work.

Basically there's a Doom 3.msi file with a line like this:
VersionNT=502

To make it work in Windows Server 2003 it needs to be changed to:
VersionNT=503

I'm uploading a file with this already done HERE.

You'll then have to burn it to CD1. I won't go into the details of copying the disk here cause if you're using win2003 and don't know how to copy a disc you'd better format and install XP!