Doom3world

If removing all Doom3 registry entries doesn't help you, then do this:

- make a shortcut to your D3_1_1.exe (D3_1_2.exe)
- in the properties window add /a parameter (so it looks like this: "X:\...\D3_1_1.exe /a"), that way you are running this executable with administrator rights
- run the patch, it will ask you where to create server image of Doom3, just type something like "X:\Patch" and hit install button
- go to the location you've just created, there will be more folders inside (Program Files\Doom 3\...)
- copy everything from patche's Doom 3 folder to your actual D3 folder
- overwrite all

Voila!

Same method applies to every InstallShield Setup Launcher under Windows 2000/XP environment