AAAInventory System by blade.dk
Details about the system:
It has a main menu where you can drop items from and equip items to.
It has an equipment menu, where you can equip up to 5 items (Head, Armor,Weapon, Shield, and Accessory), that will give bonuses when equipped, even if you are not on that page.
It has a backpack that can contain 4*any number items, so you can have more items on your hero.