Download this Famitsu-flavored edition of this Dungeon Explorer demo.
1. Download the demo zip file.
2. Extract the contents of the zip file.
3. Connect your PSP to your computer using a USB cable.
4. Go to the PSP/GAME folder.
5. Copy NPJG90011 folder into the GAME directory. Make sure there are no sub-directories in this folder.
Via PSP Fanboy