Shivering Isles Problem...

[The Black Arrow]

I have installed Shivering Isles, and I pretty much know what happened, so I am looking for a way to fix it.

I recently deleted my Oblivion Game Data to fix a previous problem, and when I loaded my last save game, the doorway to Shivering Isles was missing and all of my SI main quest items were gone (along with other quest-essential items). So I started to panic. I ended up re-downloading SI and then installed it again so I could play it. Although my keys to Mania and Dementia were gone, I could still go through the gates. But, none of my SI quests were in my journal (even though when I talked to Sheogorath, he spoke as if he had already given me the essentials I needed and shoo'd me away. Basically, he acted normal. Haskill as well. I was the only one confused and lost) when I got back to SI, and now I cannot complete a quest because an essential item no longer exists. (The Attenuator, of Judgment; I don’t have it, Sheo doesn’t have it…It’s just gone. I dare not tell him…he’ll kill me.)

So my question is this:

How do I restart the entire Shivering Isles expansion? I am pretty sure I can’t get the quest items back, so restarting is my only option. Thankfully I didn’t get very far and Ill be happy to have my Skinned Hound back anyway. =)