PCSX2 is a PlayStation 2 emulator for Windows and Linux, started by the same team that brought you PCSX (a Sony PlayStation 1 emulator).

The PCSX2 project attempts to allow PS2 code to be executed on your computer, thus meaning you can put a PS2 DVD or CD into your computers drive, and boot it up!

The project has been running for almost seven years now, and since it's initial release has grown in compatibility. From initially just being able to run a few public domain demos, it's current state enables many games to boot and actually be perfectly playable.
PCSX2 is a complex program, but thanks to it's plugin system and GUI, not impossible to use, even if you are relatively new to emulation. PCSX2 does however require a real PS2 BIOS to run. You must obtain this from your own PS2, as the BIOS binary is copyrighted by SONY and cannot be distributed with PCSX2 as this would be highly illegal. This is perhaps the only technical thing you will have to do to get PCSX2 running games, but there are guides and tools out there to help you do this (see the downloads section for tools).

It is the aim of the development team to eventually make PCSX2 compatible with all PS2 games, and all PS2 features (including the backwards support for PS1 games).

Whilst PCSX2 is capable of playing 'backups', it is not the intention of the authors to provide a means to play illegally copied games. It is however the intention of the authors to let you play (once hardware is capable) PS2 games on your PC's, with the enhancements emulation allows, such as save-states, high resolution graphics, infinite memory cards, cross-region support etc.
System Requirements :
Minimum
• Windows XP/Vista or Linux 32bit/64bit
• CPU that supports SSE2 (Pentium 4 and up, Athlon64 and up)
• GPU that supports Pixel Shader 2.0
• 512MB RAM
Recommended
• Windows XP/Vista or Linux 32bit/64bit
• CPU: Core 2 Duo 3.2GHz
• GPU: GeForce 8600 GT or better
• 1GB RAM (2GB if using Windows Vista)