Upir is correct - most of the old legends make no reference to Vampires drinking blood - it is the life-force or vitality they drain.
as for undead vampires - i've seen one. many years ago i hung out with a bunch of friends who all seemed to congregate at one flat. we all felt drawn to it, even though it was small and damp, and totally unsuitable for a meeting place. we didnt go out - we spent all our time talking to each other and sleeping over. we slept a lot - more than ten hours a day, and never felt refreshed from our "rest2, but rather weaker and drained. some slept even more - 12 or 14 hours a day. it was as if we were gripped by a creeping lethargy that seduced us.
then, one evening, when i felt fed up of it all, i decided to go home, and saw something in the hallway. it looked like a large glowing blob or mist, but made of coloured light. it was shaped like a butterflies wings, and looked very beautiful, but i sensed it was malign. it flew (or glided, it did not flap it's "wings") straight up the stairs at me, and flew over my head as i ducked. i ran down the stairs, and before leaving the house, glanced up at it. it seemed to flicker with anger, and swooped down at me. this time i did not duck, and experienced a strange feeling as it seemed to pass through me. i felt a brief struggle within my mind, then it flew away again in panic.
the next time i returned to the flat - i was prepared. i engaged it in psychic combat, and defeated it. after that, it was as if everyone had come to their senses - people came less and less, and started to get on with their lives again. the small group of friends disbanded and put the place behind us. i did hear that the girl who rented the flat died in a road accident a few years later, but i dont know what became of the others.
whatever that malevolent spirit was, i would call it a vampire - it fed of our energy,
