I think there in lies the answer. You need to keep the file path the
same. In other words you need to have the folder named "models", not
"models2". Because the model viewer needs to load everything
(animations/skins) and that specific models skin/animation isn't
located in the "models2" folder, but in the "models" folder.
And you need not worry about destroying the [root]\half-life
2\hl2\models folder because steam will pop any "needed" models into
that directory. What you need to do is back up that folder (just in
case), then extract all those HL2E1 models into that directory.
Posting And You