There is a way to become a vampire with no expansion packs.
1. First, you download a mod from modthesims.info a mod which unlocks all thehidden traits.
2.Enter the testingcheatsenabled true code.
3.Choose a household sim and hold shift while clicking, it should appear 'Modify traits for active sim
4. Click on it and choose Vampire as a physical trait.
If the mod is installed correctly, the sim's skin will become white and the eyes will glow. The needs will be purple and you can't stay much in the sun.
Hope it was helpful.