: Right-click on Part 1 and select "Extract Here" using a program like WinRAR or 7-Zip. It will automatically pull data from Part 3 and the others to recreate the original file.
You must have all parts (Part 1, Part 2, etc.) in the same folder to successfully extract the full ISO file. How to use this file sc23991-TLARSv120.part3.rar
: Once extracted, you will likely have a .iso or .bin/.cue file ready for use with a PS2 emulator like PCSX2 or for burning to a disc. : Right-click on Part 1 and select "Extract