Arcanum is actually pretty stable for a Troika game, but as anybody who's played it knows, there's tons of minor bugs, unbalanced items and quite a bit of unused content which simply never got patched or enabled.

Fans to the rescue. Thanks to a modder named Drog, we not only have a fully working widescreen patch, but a huge fan patch that fixes tons of issues. And the great thing is, it adds nothing that wasn't already in the game, just re-enables some things that seem to have been accidentally left out, like extra dialogue options, voice clips, and items.

WARNING: While I and many others have played through the game with these patches, they are technically unofficial, and the modder in question has said he is finished with Arcanum modding, so expect no support. Also, you MUST apply them before you start a new game, to avoid issues with incompatible saves.

Apply these in order from top to bottom:

The latest version (12/28/2009) of the fan patch. Essential. Must have. Get it here.
http://www.terra-arcanum.com/downloads/arcanum/fixes/UAP091225.exe

High-quality townmaps (Better looking in-game maps, also fixes some potential missing map errors):
http://www.terra-arcanum.com/downloads/arcanum/fixes/HQ_Townmaps.exe

And the High Resolution Patch. Weidu-based, so follow the directions to set it up for your system. Will allow you to run Arcanum at pretty much ANY resolution, provides an optional "compact" UI and optional high-res fonts:
http://www.terra-arcanum.com/downloads/arcanum/highres/HighRes1.1a.exe

Version: 1.5.1 (October 4, 2019): http://terra-arcanum.com/drog/uap.html#download

And that should set you up real nice. If you want more info on Arcanum, or any of the other Troika games, head to http://www.terra-arcanum.com and have a look around. Note that they also have some other mods and things for Arcanum, but most of them significantly alter the core game, or are incompatible with the UAP bugfixes. You might want to give the high-quality music patch a spin, but the original music sounds excellent and I wager you won't be able to tell much of a difference. For the purest and most hassle-free experience I recommend you stick with these patches for your first playthrough.

EDIT: If you have any problems with not being able to download, try refreshing the download page, or try the alternate links at this forum post (thanks sanpats), or for the 91225 update and High-res patches try these alternate links, courtesy of Petrell: UAP91225 update and High-res patch.

EDIT 2: Removed old patch version, as apparently version 91225 is stand-alone. Vagabond says it is anyway. Blame him if it breaks.

EDIT 3: Removing contributed torrent link due to torrent site jumping the shark.

It will if you use the UAP. If you try to use just the Widescreen patch with a cracked version it might not work correctly.

In what way doesn't it work? What happens?

I would, it's really not a big deal, like one extra model and a few items or something.

Ah, so nothing like those crazy Infinity Engine patches.
Thanks for the links. I'm looking forward to playing this. ..after Mass Effect 2 probably.

The links take me to the correct page to download the files but every time I attempt to download the file the download link takes me to here:
http://terra-arcanum.com/downloads/badlink
Any ideas what I am doing wrong?
Thanks
Just to be clear I am talking about the High Quality Townmaps and High Res Patches. I was able to get the UAP from another place.

Use the forum link in the 2nd post in this thread, they have up to date links for the other patches.

The terra-arcanum.org links are only good for one download, if you notice the disclaimer on the download page. You have to reload the page to get a new one if your first one failed.

Yeah, I saw that. I've tried a few times after refreshing the page and they just won't work for me. I'll try it on a different computer and see if some add-on in firefox is messing with it.
Thanks for the help.
Even without the patches it is so good to be playing this game again :)

I had the same problem using Firefox and a download manager (downthemall!).
They worked fine using the normal browser downloader.

I'm also hosting UAP and High res patch so you can try these links instead:
Unofficial Arcanum Patch Version 091225
Arcanum High Resolution Patch Version 1.1a
Here's also readme for UAP and it's extra content component:
UAP readme
UAP: Extra Content readme
Unfortunately I can't host the high quality town maps or lossless soundtrack because I don't have enough space on my site.

The only download that gave me real issues was the HQ Town Maps. It wouldn't download for the longest (no matter how many page refreshes), and then when it finally did the archive apparently got corrupt. Ah well, I have the rest of the important mods.

I downloaded all the mods from phanboy4's first post and installed them in the order he suggested.
Two hours of game play with no issues with my GOG install and the mods.

Just got the highres patch from Petrell, thanks for hosting it!
Played the game for several hours last night with no issues at all. Except that once again I can't seem to play a magic user, a gun-toting, fast talking gnome is just so much more appealing to me for some reason.
Thanks for all the lnks.

It seems the download site will only let you have one active download at a time, or at least I wasn't able to download the HQ maps until the music file was done, then it worked fine...

Thanks for these links! I am totally applying them now. Cannot wait. One of my favorite RPGs....yah know.