Save at the "Altar of Fire" before the final battle.

put the save in ...>My Documents>NBGI>DarkSouls>FairLight>DRAKS0005.sl2

In the game, all the bosses have been killed, all the secret walls have been revealed, all the titanite and a large amount of armor/weapons have been collected, which by the way have been pumped to the maximum - save at the “altar of fire”