Run UDKEditor.exe . The first launch takes 3-5 minutes to build lighting caches. If you see a black viewport but the UI loads, restart once—that is a known July 2011 bug.

Many commercial games shipped using the July 2011 UDK codebase. If you are a modder trying to extract assets from a game like Dungeon Defenders (launched late 2011) or The Ball , you need the exact editor version that wrote the package files. Opening a .upk file from this era in a newer UDK (2012 or later) will often crash or fail to parse.

Treat as a time capsule. Install it for the nostalgia of the "UDK splash screen"—the one with the generic sci-fi soldier and the Gears of War-esque COG logo. Compile a script. Rebuild a room with BSP brushes. Let it crash when you add too many dynamic lights.