The Elder Scrolls IV: Oblivion/Being a Vampire

In your adventure you will meet many vampires and you may receive the "porphyric hemophilia" disease from them while you're fighting with them. You can cure it with either a spell/potion cure disease or using an altar in a church.

If you don't cure the disease within 3 days, when you sleep you will slowly become a vampire. This change is irreversible after you sleep and will take some time to clear up as it involves a quest.

On the first day after you get the disease and you waste 24 hours and go to sleep for 1 hour you will receive these effects
 * Strength,Willpower and Speed go up 5points
 * Acrobatics, Athletics, Destruction, Hand-to-Hand, Illusion, Mysticism and Sneak skills go up 5 points
 * Resist Disease and Resist Paralysis 100%
 * Resist Normal Weapons 5%
 * Receive "Hunter sight" (combination of Night Eye and Detect life) Duration: 30 seconds
 * Weakness to fire 20%

If you waste 24 hours and sleep for 1 hour again you will get these effects:
 * Strength,Willpower and Speed go up 5points
 * Normal Weapon Resist 10%
 * Receive "Vampire's Seduction"+disposition(charm)50point for 20secs once a day
 * Sun Weakness:receive 1point damage every 1sec while outside in sunlight
 * Weakness to fire 30%

If you waste 24 hours and sleep for 1 hour for the third time you will get these effects: ->Strength,Willpower and Speed go up 5points ->Normal Weapon Resist 15% ->Receive "Reign of Terror"stop enemy from using spell and make lv6 or lower scare for 60sec use once a day ->Sun Weakness: receive 4 points of damage for every 1 sec while outside in sunlight ->Weakness to fire 40%

If you waste 24 hours and sleep for 1 hour for the fourth time you will get these effects:
 * Strength,Willpower and Speed go up 5points
 * Normal Weapon Resist 20%
 * Receive "Embrace of Shadows"Night Eye 90secs Invisibility120sec
 * Sun Weakness:receive 8point damage every 1sec while outside in sunlight
 * Weakness to fire 50%

A Vampire Cure
To start, you will need to talk to a priest or Vincente Valtieri of the dark brotherhood, it is best to talk to them both if you can as after you finish the quest you can still ask for a cure from Vicente even though you have cured it, making an uncompletable quest.

Note: If you have the PlayStation 3 Game of the Year edition, there is a major glitch that doesn't allow you to complete the quest to cure yourself of Vampirism. This glitch is only found in the Game of the Year edition for PlayStation 3—no other versions of the game have the glitch.