Half Life 2 isnt out, about 2 months ago someone hacked into Valve who the company who is making it stole all their source code, gfx etc from that time. The you could partialy play some levels and look around but in no way there was a complete game there.. so they are selling this stuff.. the game isnt due out till prob april or summer.. and there iS no demo of this game yet.
here are some screen shots of the real game..
http://www.planethalflife.com/half-life2/screenshots/
remember its not out yet in stores.. and prob like 70% done with that russian crap..