Madman's right, 1.1 was designed without Steam and probably won't work with it.
If you really want to play 1.1, the reversed pack will work fine. ESF-world don't seem to have the original installer for 1.1, but as long as you plan to use Steam, it shouldn't be an issue. If you manage to find the old 1.1, remember that your Steam-copy of HL won't support it and that you would have needed to install HL from CD without Steam.