I finished Thief II The Metal Age today and I excitedly jumped into Deadly Shadows only to realize it doesn't run well. The games isn't smooth enough for me to play without feeling a headache coming on. I'm not sure what the issue is. My computer has run literally everything I've installed on it, including Crysis on high settings.
Is there a setting that I can change or a mod I can use to make this game run smoothly? I'm really disappointed. Until I get this fixed I'm going to be playing The Dark Mod, I guess. Or maybe Thief The Metal Age x.

Thanks in advance.

What are your computer's specs? Processor, graphics card, etc. Is the problem just low framerate, or are there other graphical glitches?

It's possible that a certain graphics option is causing problems, like one of the lighting settings, so try fiddling with those in the options menu. Also make sure that you've got the latest drivers for your graphics card.

There are very small graphics problems. So small, in fact, I think they are just normal glitches in the game.
It seems like it's just low frame rate, I guess.
I also can't find a way to adjust the sensitivity of the mouse. It's so sensitive that I have trouble aiming sometimes.

Operating System: Windows 7 Home Premium 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_gdr.120830-0333)
Language: English (Regional Setting: English)
System Manufacturer: System manufacturer
System Model: System Product Name
BIOS: BIOS Date: 07/15/10 20:15:05 Ver: 08.00.15
Processor: Intel(R) Core(TM) i3 CPU 540 @ 3.07GHz (4 CPUs), ~3.1GHz
Memory: 4096MB RAM
Available OS Memory: 3960MB RAM
Page File: 3518MB used, 4397MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
Card name: ATI Radeon HD 5700 Series


*edit*
Another issue. I thought I had fixed this, but I guess not. I just tried to load a save and the screen didn't do anything and the music stuttered continuously until I force the game to close. This has happened before and I had to reinstall it.
*edit2*
Running as administrator helped the save game issue.

I just updated my drivers.
I also just found out I can't buy anything in stores in-game...
How is it that I played through Thief 1 and 2 with no issues and then I put in Deadly Shadows and I've had so many issues?

You have to fence your loot to get money to buy things in stores. Even when the loot you found was coins, you still have to fence them first, which doesn't make any sense. Also, you can only carry so many of each type of item, so if you're full up then you won't be able to buy any more. Perhaps one of those is the issue? Well, there's a long history of fan fixes for Thief 1 and 2. In fact, one such fix is included in the GOG versions. Ad then, there's a totally new one (presumably based off of the recent Dark Engine source code leak) which is available in the sticky thread that gets both games working on modern systems even better. Thief 3, on the other hand, doesn't have as many fan-made fixes and stuff. It's more recent, so it usually runs OK but it has issues with admin rights (as you found out, you have to run as admin) and maybe a few other glitches with newer hardware.

By the way, did you INSTALL the game as admin? If not, it might be worth uninstalling and reinstalling as admin (and of course running as admin). Back up your saves first.

I have enough gold or whatever for it but it won't let me purchase anything. I have roughly 5000 gold and I can't even buy a water arrow. I left click and nothing happens.

I can't remember if I installed it as admin. That thread was able to get the FPS to look much better. I set antiAliasing to controlled by application and turned bloom off and that seemed to fix it. I need to be able to bu stuff and then I'll be happy. I have so much money and I can't spend it. I'm a little pissed that the climbing gloves aren't given to you start of the game, actually.

*edit*
I really appreciate your help. I'll mark your post as the answer to my question and hopefully I can get the other issue fixed.

Glad you got the FPS fixed. I've never heard of that problem with buying items... if you can't figure it out, a reinstall as admin might be worth trying. That's the only thing I can think of. Anyone else have any ideas?

I figured it out. What I did was reinstall as admin and then install Thief Deadly Shadows Tweaker and THEN run as admin.

Awesome! Glad it's all sorted out. Enjoy the game!