From the "Where is my Library stored?" FAQ
The Core Library contains Live's factory content and can't be changed by the user. It is tied to the Live installation, so you don't need to worry about this.
On Windows, the Core Library is stored under C:\Users\ProgramData\Ableton\Live 9\Resources\Core Library.
Totally mind boggling, especially considering that this directory doesn't exist in Windows 7.
There is of course "C:\ProgramData\Ableton\" yet on my system this only contains "Live 8.2.1" and "Live 8.2.2". Seems some of the old Live installers didn't clean up their mess back then.
Another place for common data is "C:\Program Files\Common Files\" yet this also doesn't have a folder called "Ableton".
On my system the core library sits in the program folder. And I'm pretty sure the same applies to some other users as well. So, the folder where you installed Live to. This will contain a sub-folder called "Resources" and that one contains "Core Library".
Its been a while since I used it, but to my knowledge Windows 8 doesn't apply changes in software location. Not 100% sure, but to my knowledge the same applies there; C:\Users\ProgramData doesn't exist.
This really looks very sloppy on the part of Ableton IMVHO.