Last year, I installed Thief 3 on Windows 8 with the Sneakly Upgrade with no problems.

Recently, I tried installing Thief 3 (With the new version of installer, v2.0.0.6 I think) on Windows 8.1 and it crashes to desktop instantly, regardless of whether Sneakly Upgrade was installed or not.

Really need some help with this.

report everything in the sneaky update topic on TTLG. include all the details and specs you can think of.

Same issue here. With or without Sneaky Upgrade, nothing happens...

If you do not get a better answer, then it could be something to do with the scaling change win 8.1 made. If you find the exe for Thief 3, right click on it, then select "Disable Display Scaling On High DPI" on the comparability tab, well it is something to try. I had to do this for another game.

Nope, tried 'Disable display scaling on high DPI settings', run as administrator, and all XP, Vista, 7 & 8 compability. All of the above methods doesn't work.

Had a similar problem on my laptop with Intel and NVIDIA video adapters. It crashed in Intel display driver (igdumdim32.dll). Curiously enough, changing settings in NVIDIA control panel to prefer integrated adapter helped. Might be some issue with collaboration between drivers.

If you're having this problem on an Optimus (Nvidia/Intel) laptop, then try updating the Nvidia driver - installing 340.43 (beta) fixed it for me. There's still a crash on exit to the desktop but not on level load, fortunately. (Updating the Intel driver to the current beta didn't improve this.) Of course, reverting to an older driver may fix it too.

If a driver update doesn't help either run on the Intel graphics as izbyshev suggests, or (as a last resort) run in windowed mode.

I don't know much about tech stuff, but Win 8.1 broke many games for me. Win 8 was ok.

Oddly, after putting the compability mode on Windows XP SP2, it works, even though it can't a few months ago. Strange.