I'm just trying to figure out some of the game mechanics.

If I'm in a room in a house and the door of that room is shut and I kill someone in there does the town immediately know I have done that?

I'm assuming that there is a shout by the NPC and people in the house are alerted and in turn alert the guards etc... If that person is alone in the house and you can 1 hit kill them, will the guards know it was you?

Also, the same applies to stealing....again, in a room, this time on my own, if I take something do people already know? Do I have to be in sneak mode to steal the item?

And again, locked doors....no one is around I pick a door, do people know? If someone walks in and the door is open and I'm in the locked room does something get flagged?

I'm trying to understand the mechanics of how this works, if someone can enlighten me that would be great.

Thanks all in advance!

No what happens behind closed doors, provided there is nobody else in the room to see it, doesn't net you a bounty... However if someone does see it you can avoid the bounty by killing every witness that is there before the guards arrive as if all witnesses are dead then nobody knows you commited a crime in the first place... Luckily there are no CSI's in The Elder Scrolls universe...

As a side note though, this only works this way if you kill them in one shot... If it takes a second hit to kill them and there are other people around then you're hosed...

Ok, that's grand. So kill everyone before the guards turn up and I'm good.

Another question off of the back of that. If I get a large bounty that I can't pay I go to prison. How long do I stay in there and can I escape?

as long as nobody sees you, you dont have to be in sneak mode to steal stuff, but people tend to look at you more often when you are just walking around....