DOOM 3 will in fact install and run on Windows Server 2003, Windows 98, Windows 98SE, and Windows Me. You can get the updated (and unofficial) installer here:
http://www.cyberfight.org/ft_file.php?ft_id=572 Alternatively you can just as easily manually install DOOM 3 on these operating systems All you need to do is create a directory [COLOR=Sienna]/Doom 3[/COLOR] (where ever you want it, create a base directory [COLOR=Sienna]/Doom 3/base[/COLOR], then copy the PK4 files to the [COLOR=Sienna]/base[/COLOR] directory and the exe to your [COLOR=Sienna]/Doom 3[/COLOR] directory. You can also copy the [COLOR=Sienna]/Docs[/COLOR] directory to [COLOR=Sienna]/Doom 3/Docs[/COLOR] if you want to mirror image the id installed product.
If you use these exact paths, spellings, and case settings you'll have a mirror image installation of what the id Software installer offers, sans a pile of uninstaller crap in your registry. You can easily create exact replicas of the default installers icons as well; the default game launch icon is "Doom 3" (exact case and spelling) and is typically linked to "[COLOR=Sienna]C:\Program Files\Doom 3\Doom 3.exe[/COLOR]" and the default help launch icon is "Documents" (exact case and spelling) and is linked to "[COLOR=Sienna]C:\Program File\Doom 3\Docs\help.htm[/COLOR]".
People with limited system resources and/or systems near or below the DOOM 3 minimum system spec will find the game performs better on Windows 2000, and even better on Windows Me or 98SE. Low end systems, slower CPUs, less then 512 system RAM and/or slower video cards Windows ME/98SE will probably offer the largest performance boost. There is quite a bit of tweaking though that has to be done to how this older OS manages memory, drivers and cache but you can eek every last iota of performance out of your hardware if you're patient. Axcel 216's Site:
http://www.mdgx.com/ ...offers excellent guides and tools to tweaking the every ounce of performance out of the Windows 9x platform. For the less patient, or inclined to tweak their OS settings the abandoneware program. Alternatively; Tweak-Me Gold (Google) offers a safe, easy, fool proof interface to many advanced tweaks, works with both 98SE and Me, and can be found on many file sharing programs like eMule (Google-A-Rooni - do exact "Tweak-Me Gold" searches with quotes).
Don't assume that just because Windows 99SE/Me are old they are a technically inferior OS choice. They are lean & mean operating systems that expose a lot of the OS API for tweaking, don't install a lot of commercial marketing and shovel ware, consume minimal resources of RAM, HD space and are very easy to tweak, repair or reinstall when things go wrong. On lower end hardware it's not uncommon to see game performance increases of 20 to 30%. A lot of game fans that had to have XP because it was hyped as the latest and greatest adopted it the cost of sacrificing a lot of game performance.
DOOM 3 fans with a fat wallet that want the most performance where cost is no object, or that have a high end system above the DOOM 3 minimum spec and want to get the most of of it will probably want to use or try Server 2003. Server 2003 has a more modern kernel then XP (even with SP2), and a better memory manager, and will run the game faster on some systems. You'll need to follow the instructions in Windows Server 2003 As A Workstation:
http://www.msfn.org/win2k3/ That done you'll end up with an OS that is not only boots, runs, and runs games and applications faster and more robustly then XP it's a more secure OS. If you want to try Server 2003 to see if it's right for you you can download a free Microsoft Trial of here: