Can someone help me kill SMough and ornstein! I'm level 45 undead warrior.

Yes, you can walk back. Take the staircase up to the roof and go down on the other side. Keep going and you'll find a room with the Silver Knight Armor set. The door to that room (it's across from the Havel room) was previously locked, but you can lock it from the inside out. Once you unlocked that room, go through it and take a right when you get at the top of the small staircase there. You'll end up in an enormous room with two Giants. Go downstairs and LEFT (on the right you'll find the fog door to the hardest boss fight in the game) and just ignore the giants. Run through the room until you reach the door. There should be a mechanism to unlock it on the left side. Once you open the door you should realize where you are as you've been there before. Just head straight and you'll end up back at the first bonfire in Anor Londo. Another possible route is through the Giant Blacksmith. Get in the huge room in the cathedral and cross over to the other side. You'll find a stairway leading down to where you'll find a blacksmith. Go past him and unlock the small metal gate, and you'll find yourself on your way to the first bonfire in Anor Londo again. Go back to where the gargoyle things drop you in Anor Londo for the first time and they'll take you back to Sen's. Then just go down through the cage elevator and make your way back to the Undead Burg, where you'll be able to find Havel. Did you pick the Master Key as your starting gift. And don't listen to Capiton. You need the master key (not the residence key) to enter through the top entrance, and the key to the bottom entrance you'll find after killing the Moonlight Butterly in the forest. And you're a level 41. Havel should be a piece of cake at that level. And get the idea of people helping you or trading items with you out of your head. That's not how the game works.

You can walk back, just go to where the gargoyles drop you, and they will return if i remember correctly, or use the bonfire to go there. The havel wring is in a tower, there are two ways to get it. You can go back to the bridge with the dragon, where the knight is who praises the sun. A locked door there will get you to him, and if i remember correctly, the key can be bought from the sales man in the undead burg. Or where the hydra in the lake resides, is the back entrance to where the mob with the ring is, cant open the door from the outside. But heres the trick, walk to the door, strike and back off, the mob will sue the club and swng on him through the door to hit him. Keep repeating until he is dead, but be careful, he is usually a one hit kill.