Download the new Odin3_v3.04 a new flasher tool forIII, the successor of Galaxy S2 that has launched world. The Odin3_v3.04 is the default PC application that can be used to manually install or flash ROM, Kernels, Modems and Custom ROM. If you are an advanced user and an expert of tweaking Galaxy S3 firmware, you need this to enjoy more of your device.
Download Odin3 v3.04
This is also useful to fix soft-bricks by flashing the stock ROM, you can read a full detailed guide on how install Stock ROM here: How to Install Samsung Galaxy S III Stock ROM