When you are doing the mission for the vampire cure see the count of Skingrad after you talk to the guy in the mages guild. He will tell you that he needs a vampire cure for his wife and that you should go to this witch. Go to the witches house (follow your map marker)she will tell you that she needs 5 grand soul gems (you can buy one each at a mages guild in every town). After you get the soul gems return to the witch and she will ask you for the following ingredients garlic, nightshade, blood grass, Aragonian blood,and Vampire ash (not form a regular vampire)to get the garlic go to Skingrad and break into one of the mansions and then go to the basement you will find garlic clusters and use those for the garlic if theres not enough then go the main ingredient in the Market District of the Imperial City. To get the Nightshade go to the main ingredinet. To the blood grass go to the plains of Oblivion and you should see some (if you have already completed the Oblivion gate quest then you shold find some near the ruins of the gates). After that go back to the witch and ask about the Aragonian Blood she will give you a dagger use this on any Aragonian in the game and you will get its blood. After that ask about the Vampire Ash and she will tell you to go to this cave (follow your map marker)and once your in the cave find the vampire leader he should be the green marker after you kill him go back to the witch and she will ask you to wait 24 hours. After a day or two go back to her and she will give you the 2 vampire cures use the cure right away and then go to the Castle in Skingrad. Talk to the Aragonian servant and she will ask you to follo her to a secret dungeon. There watch the cutscene. After all that go back to the Aragonian servent and shee will tell you that the count will be with you soon just sit there a while and the count will come to you. Ask about the reward and he should give you 200 gold keep asking about the reward and he should still be giving you 200 gold

NOTE- This will not work if you downloaded the patch off Xbox Live

NOTE- You can get this quest from the Vampire in the Cheydrinal Dark Brotherhood Sancturary after he bites you. He will give you the oppurtunity after complete many quest from him