Sleep paralysis?

This is an old experience. somewhat scary yet interesting...

I think I had a few experiences of something that is maybe sleep paralysis. It was a bunch of times when I was in college. I was dozing off in bed when I heard a knock on the door. I could see the door but was completely incapable of even getting off the bed. It was lousy because I used to try very hard to move until I was just fed up. After a while or so, I used to snap out of it. when I woke up a while later (and could move my limbs) I once noticed that the bed was in a different position altogether. This is how I realized that it was maybe some kind of a dream.

I had this exact same experience about 4 or 5 times. And it never felt like a dream.
As in I always thought my eyes were open since I could see the room, the bed, myself in it,
and the door in front of me.

I was never able to ascertain if someone did knock on the door.
In such a case, MAYBE this happened cause my mind(awareness) jerked to consciousness while the body was still asleep. [*sceptic]
I have read about such experiences though.

Apparently, there is a normal mechanism of paralysis that occurs when one is in deep sleep.
They say it is useful because it prevents physical movements (for most people) during a dream.

Whats your preferred messenger service?

Kindly try to drop in a word if you are passing by.
Its an informal survey for my course.

1. Google talk
2. ICQ
3. MSN live msgr
4. Skype
5. Yahoo

please write in your choice as a comment (even if its not above list).

snaps