Seemingly coming out of nowhere, an unofficial patch has turned up on French forum Ariane4ever, dragging the classics into the modern age.
While the patches are mostly meant for Thief 2 and System Shock 2, the original Thief can also be massaged into compliance. Gamers were used to a huge array of workarounds to get the Looking Glass Studios games working on modern systems, but these patches seemingly fix everything from the get go.
The fixes are legion, including swapping out codecs so the in-game movies play properly, new resolution support, 32-bit colour support, not switching resolutions between menus and gameplay, allowing larger textures, addressing audio bugs and even greatly modifying the level editor for both games, so that it can cope with the changes. They're so pervasive, in fact, that it's hard to believe "Le Corbeau" ("The Raven" in French), the patch's author, doesn't have access to the source code. We're secretly hoping that this is the passion project of someone at Eidos Montreal as they work on Thief 4.
For the monolithic change list and downloads, head over to TTLG to get your classic gaming on. You'll likely still need to know a few workarounds to install the games in the first place, which TTLG also provides.