Lol! Did he just ask who g-man was!!!?

Dude, nobody knows g-man's real id and what his motives are. Just know this, he hired you for this job...and just clock the game without questioning, ending of Half-Life 2 and the episodes will give you more answers about him as well. Also, if you can, play the first game, though he is as vague as he is in the second game.

I have a feeling that OP is a Valve hater.

I have AMD Athlon 3000+, 1gb ram and 4400MX 128mb gfx card. I can play Half-Life2 not even the lowest setting but bit better with absolutely no problems, including online!