A "repack" usually means a third-party, unofficial modification of the original driver installer [1].
After installing the repack, create a System Restore point. Name it "R420 Working State." Then, turn off driver updates via Windows Update (use the wushowhide.diagcab tool) to prevent Microsoft from overwriting your working repack with a broken default driver. spd driver r420 download repack
When an official driver no longer exists or is inaccessible, these sources have a better reputation than random uploads: A "repack" usually means a third-party