This happens when your Windows user account lacks permission to alter system registries.
To have all the cards available, players must choose the "Full Deck" option in the last game (Joey the Passion). Yu-Gi-Oh! Wiki Contributors to Yu-Gi-Oh! Wiki
You download a completed save file (usually named system.dat or deck.ydc ) and place it in the game's installation folder (Commonly C:\Program Files (x86)\Konami\Yu-Gi-Oh! Power of Chaos... ).
Unlocking all cards in Yu-Gi-Oh! Power of Chaos offers a wealth of benefits, from increased deck-building flexibility to improved competitive edge. By using the methods outlined in this article, you can unlock the full potential of the game and experience the thrill of dueling with any card you choose. Whether you're a casual player or a competitive pro, mastering Yu-Gi-Oh! Power of Chaos has never been more accessible. So why wait? Unlock all cards today and unleash your full dueling potential!
Rename your existing system.dat to system.dat.bak just in case.
You may need to edit the registry ( regedit ) to ensure the CommonDir in HKEY_LOCAL_MACHINE\SOFTWARE\KONAMI\Yu-Gi-Oh! Power Of Chaos\system points to the folder containing your "all cards" system.dat file.
Joey the Passion features the largest card pool (350+ cards) and is backward compatible with the cards from the previous two games.
If the game crashes upon reading the new save file, right-click the game shortcut, go to Properties > Compatibility , and set it to run in Windows XP (Service Pack 3) mode.