Hi, I noticed a few threads about issues with getting Thief games to run on modern windows. I still run Windows Xp and found out that you had to shut down the core affinity of your processor to make the games run. This is a simple process, does not harm to your system, as it all switiches back on the next time you reboot. Essentially modern processors run on 4 ( sometimes 6 cores ).

So boot up your Thief game, leave it at title screen, then minimise it.
(For windows XP )
Press Ctrl+Alt+Delete to open Windows Task Manager, and go to the Processes tab and look up for the process name that you want to set the affinity for. In this case select one of the Thief games you can see running on the list and right click it.

Choose the option from the menu that says " SET AFFINITY".

A "Processor Affinity" window opens. simply untick CPU 1,2 & 3, leaving "0" ticked.
Then press ok.

Go back to your game and it should play without issue.