Alright so after i lost some time messing with files and stuff, YOU CAN actualy play on Steam with your old account and on top of that you dont have to re-download the 60GB of the game again you can just cut and paste the game folder to the steam folder then with the Steam Library open righ-click on the game, Properties and on launch options you add " -provider Portal " without the ", launch the game let it update and have fun, hope this helps some veteran and new players.
Cheers.