Unchecked content upon first install! Where is it now?

[LordOfAwe]

After I bought Portal 2 through steam app I went on to install it. (nothing new till here).
On the install screen there were three checkboxes relative to game content, I was a fool (it seems) to uncheck some of them, thinking I could install those later.
Now I cannot find how to install those. And I don't even remenber what those checkboxes did say.
I tried uninstalling the game through the control panel, but upon reinstall, the checkboxes dont appear anymore.

Any help will be greatly appreciated.

[StAASN]

When i bought it 2 days ago and tryed to install I didn't get any 3 checkboxes besides desktop shortcut and all that. Maybe you need the Source SDK tool or something idk but I'll try to help at least.