from what i gathered around the net it seems that this 700 Mb hl2 file is the hl2 tech demo valve showed us at e3.

its meant to show us the phisiques of the game

so this file is more likely to be that working tech demo itself

i wish smone has finished the DL to give us some more info on that,personally my DL job hasnt finished yet.

this is the pic cliamed to be from the 700 Mb hl2 file: