Does anyone know why Thief must be run as administrator in order to see videos? Which specific rights does Thief need (so I can give them to my regular account)? The problem I have is I'm using a Logitech G5 mouse and SetPoint doesn't work when a game run in administrator mode. So running Thief as administrator is not an option for me.

Hello :)
Sorry for my bad english i am french.
here is the solution that has functioned for me :
DL http://downloads.ttlg.com/download.aspx?id=2461 and execut it with administrator mode
open a 'command prompt' using a rightclick, select, 'Run as Administrtor'
type: cd C:\Windows\SysWOW64 (32bit users can skip this step) - press enter
type: regsvr32 ir50_32.dll - press enter
Run thief2.exe with administrator mode

the intro video does not start automatically but just click on "the intro" to watch it.

to undo what you have done, type: regsvr32 /u ir50_32.dll
there is an error during unregistration, but it does remove it from being active

waiting your feedback :)

This was my case too. I found out that ffdshow codecs package i had installed caused the game to crash during animation. After its removal it started to work fine.