So I've tried to install the copy of Thief I just bought and it didn't work. Not a problem I thought, since this happens often with older games. But after using the lgntforce command on the Run menu it still gave me the same error message. Every FAQ I've read says that this command should take care of all the installation problems, so is it just my computer?
Your best bet would be to head over to ttlg.com and check there. They've got a lot of information on getting the Thief games to run. I've been able to play all three of the Thief games on Windows 2000 and XP and with a number of hardware advances so don't give up.
After much inquiry and headache, I finally threw in the towel and bought the XP-compatible Thief Collection, which was published in the UK and includes all three games. Currently playing the first game and loving it. The best part is it was only around 25 bucks on eBay.