Instructions
Locate the model number on the sticker on the bottom of the PS3.
Look for a model number that begins with a "CECHE" on an 80GB PS3. This PS3 version will play PS2 games by using software emulation, which means that most games will play without any problem. A few will have graphical glitches.
Read the model number and see if it begins with "CECHC" on a 60GB PS3. This version plays PS2 games through software emulation.
Search for a model number that begins with "CECHA" on a 60GB system. This version has the PS2 hardware installed into the system and every PS2 game will work like it does in a PS2 system.