Thief 2 won't let me play without the CD

I have a UK version of the game and have downloaded two different patches; the replacement Thief2.exe file and the Knacker.exe file. I'm not sure if I'm doing it right, but with the knacker.exe, I copy the files directly and overright existing files. But then it doesn't work at all, even with the original CD. The other replacement thief2.exe still asks for the original CD, fine, I'll put it in, but I prefer to play without it. Can someone please help me.
Thanks.