Everytime I start the game the intro videos run fine and the first menu screen works, however as soon as I click on options or load game or new game the game crashes with the sound getting stuck in a loop. HOWEVER if I first start the game and then immediately exit it, then start it again, I can play normally.

Now I've tried the Sneaky Upgrade, it didn't seem to work any better. Also tried Thief: Deadly Shadows tweaker v1.2 but that caused more problems than it solved. After trying both of these (not at the same time) I re-installed and now I'm stuck with a game a have to start twice in order to play, which isn't horrible, but is mega-annoying.

Any ideas?

EDIT: Fixed it, somehow, not sure what did it. I set the processor affinity as per this guide http://www2.robpol86.com/guides/ImageCFG/ and disabled my antivirus (Micosoft Security Essentials) and the game deemed appropriate to work the first time I started it. I still have a slow computer for playing the game, but hey, at least it works!

EDIT2: fixed a typo

this should fix it for good.