It isn't the best for gaming and doubt it will do well with HL2. I can play BF1942, Need for Speed Underground 2, and The Sims 2 quite easily on mine but I've never tried HL2 on it. I don't really game on my 600m as that's what my 8300 is for.
The 9000 will not play HL2, but with the 9600 mobility radeon it plays very well. You will need 1GB of ram though. 512 is not enough. Medal of honor pacific assauilt will also play but is not real good with 512mb.
The 9000 mobility is kind of like a 7500 desktop card but slightly better.
i have the pm 1.6 1gig 32mb 600m, and i can play hl2 at 800x600 absolutely fine. I tried that with 512 ram and it was choppy as hell, but when i upgraded that it ran well. So if you can live with that resolution, than go ahead and get another stick of ram and ull be fine.
btw if ur wondering, my fps with that are 50+ all the time, more than playable