Regarding patch issue, it is written in Co8 readme:
There is no need to install Atari Patch 3. The only additional feature Atari Patch 3 contains is a fix for the infamous DirectX 9.0c looting bug, but this particular issue is also fixed by the Circle of Eight Modpack. If you have installed patch 3 already or if your game comes pre-patched with Atari Patch 3, don't worry. It doesn't matter.
When you run the Circle of Eight installer, you will have an option to pick up location when it should install to (see pic attached). Click
Browse and choose the folder where your ToEE is installed. By default it will be
C:/Program Files/GOG.com/Temple of Elemental Evil If you have 64bit operating system, it will be
Program Files(x86) instead
Radiox1: ok i just read another post that said to not download the default gog installer.....and to create a games folder in c drive and download it there srry for the bother ppl i guess this is common knowledge on here
If it was common knowledge, you wouldn't read a post about it ;)
Anyway, installing in default location doesn't make the game unplayable (most of the time). But sometimes can cause some problems, especially if you have Vista or Win7.