Oh guys, could the reason you're getting 'file is corrupted' is because you're trying to extract the 3 files separately? Just wondering...
You really only need to put all 3 files in the same folder and extract the first one, Winrar or 7zip will automatically search for the other parts and extract automatically.
It's a feature of zipping programs (I'm not sure if Winzip performs this too, I never use Winzip).
If it still says corrupted when you do this then something is obviously wrong with the other parts though =x