UlaunchELF is much more than a simple file browser. It acts as the operating system for the PS2 homebrew scene.
Place OPNPS2LD.ELF on your USB stick. Boot the uLaunchELF DVD, navigate to mass: , select the OPL file, and launch it. This allows you to play games from USB, HDD, or SMB Network shares. Ulaunchelf V4 12 Dvd