Video card must be 128 MB or more with support for Pixel Shader 2.0b (ATI Radeon X800 / NVIDIA GeForce 7600 or better).
Portal 2 is not a "free-to-play" game, but it is frequently available at a very low cost through official channels: portal-2-pc-game-free-download-full-version
Pirated versions do not receive official patches, meaning you miss out on bug fixes and performance improvements. Video card must be 128 MB or more