Using USB Hard Drive as PS2 Memory Card: Not Directly Possible—Best Workarounds

Not directly. The PS2 does not support USB mass storage for game saves natively. Its USB 1.1 ports are for: EyeToy, Keyboard, Headset, Network Adapter (HDD), specific peripherals.

Workarounds

• USB Memory Card Adapters (Datel Max Memory, Action Replay Max, generic): Plug into USB port → Acts as virtual 8MB/16MB/32MB Memory Card. Save/Load via adapter's menu (hold L1+R1+Select+Start at boot). Compatibility varies; some games refuse to save to USB devices.
• Internal HDD (Network Adapter + IDE HDD) + OPL / HDL / FMCB: Install games to HDD (ISO). Saves still go to Memory Card (virtual or real). Virtual Memory Cards (VMC) can be created on HDD via OPL Manager or uLaunchELF — each game gets its own .vmc file on HDD. This is the best "HDD as memory card" solution.
• FreeMCBoot (FMCB) + uLaunchELF: Copy saves between MC, USB, HDD (VMC), PC (via LAN/SMB).

Best Modern Setup

1. Fat PS2 + Network Adapter + 128GB+ SSD (SATA→IDE adapter) or 256GB SD (SATA→IDE→SD).
2. FreeMCBoot on Memory Card.
3. Open PS2 Loader (OPL) for games.
4. Create per-game VMCs on HDD via OPL (Settings → Create VMC).
5. Backup VMCs to PC via SMB/USB periodically.

Original 8MB cards die (bit rot). VMC on SSD is permanent.