All you need is the dhewm3 source port: https://dhewm3.org/

Then get your offline installer and unzip it with innoextract: https://github.com/dscharrer/innoextract

Get the necessary files: https://dhewm3.org/#how-to-install

And throw them to the source port. dhewm3 supports mods, is easy to manage, and does not require serial keys to play, single-player or multiplayer. In other words, and in short, dhewm3 is the definitive way to play vanilla DOOM 3 with the Resurrection of Evil expansion. ;)

I'm sure the people who are complaining about serial keys are completely unaware of the dhewm3 project.

so you haven't read this thread… and probably not the others as well

Thank you for the instructions but no, not knowing about it is not the problem. I simply dont care about the project. I am a customer who bouught a product on this site and I simply can EXPECT it to work without any kind of modificatoion. If it does not they should not sell it. It is as simple as that. It really puzzles me how people can see this differently. I won't buy a car just to have to go to some scrapyard and get the parts I need to get it to run.

Also it is extremely disappointing that GOG is unable to fix this problem OR put a warning on their site since this is known.

Easy-peasy fix: use IPv6!

Keep in mind that this is a game from 2004. And just like any old game, it requires modifications here and there. Older games in general always require fan patches and source ports to work decently, and GOG has already made use of some fan patches and created its own (GOG's wrapper is an example). I would venture to say that GOG doesn't care about serial keys, because the publisher itself doesn't care about them, and they (GOG and publisher) know the source port, and know that it works perfectly well.

And speaking of games that don't work, GOG is full of them, and many, unfortunately, have no fan patches or source ports, and GOG hasn't done anything to fix them either. The DOOM 3 serial key not working is the least of the problems here. Blood Omen 2 - Legacy of Kain, for example, is completely broken in its current state, LUCKILY, there is a fan patch that does the job: https://classicrebirth.com/index.php/blood-omen-2-re -vamped/

And Soul Reaver 2 also has a great fix: https://classicrebirth.com/index.php/soul-reaver-2-soul-fixer/
SR 2 is a complete mess without this fix.

Honestly? I don't mind resorting to fan patches and source ports. I truly admire the work of these guys... They are heroes! They do more for the community than the companies that publish and sell the games.

Well - the moment they sell broken games knowingly they are no heroes - they are the opposite. They should not take such things too lightly. It's a pity that customers nowadays do. Again, if I pay for something I expect it to work and if it does not the contract is invalid. It's really disappointing that GOG does not even think this is important enogh for some feedback. Just when I thought they were getting better ....

Well, after the NSFW games started dropping here... I knew things weren't going to be good.
Side note: Errrr... I swear I tried my best not to write this. XD

But GOG is being purified by some good old games that dropped here not long ago. ;)

id Software's biggest mistake was creating limited-use serial keys for DOOM 3. Bungie was smart in this regard and created unlimited-use serial keys for Halo - Combat Evolved (2001). This means that you can install Halo as many times as you want, on different PCs, using the same serial key, to play single player mode. The same you can't do with DOOM 3 and Quake III, even if the player's intention is for single player mode only. Let's curse the use of DRM for 1 minute! XD

That's true, mate. I'm glad that GOG has listened to its customers' pleas, and is working on a fix for DOOM 3's keys. However, Quake III, according to reviews, also suffers from non-functional serial keys. Good thing Mr John Carmack was ahead of his time and made the source code of id Tech 3 available, due to this altruistic attitude, we have ioquake3: https://ioquake3.org/

Another great community effort that elevates the Quake III Arena and Team Arena experience. ;)

On behalf of all those affected, thank you!

I don't mind if gog sells abandoned games as long as they mark them as such and toss us a decent discount now and then. I agree that gog should keep up on the ones releasing games here though.

What about the other games people indicated were impacted by the same?