Walls and Ceilings - how do I determine load bearing walls

I recently purchased a home that had a temporary wall put up to divide the living room. I have found out from the neighbors that the living room was originally running parallel to this wall and that there used to be a permanent wall in that spot, that made a bedroom. I have removed the temporary wall, and would now like to remove the wall that divided the original living room, to make a large "L" shaped room. I'm not sure I can remove this second wall, because then there would be no walls supporting the back corner of the house. It is a small house under 1000 sq. ft, and at some point the house has been without one wall or the other, but never both. Any suggestions on if this is possible?

Hi ace15,any wall that runs perpendicular to your ceiling joist is load bearing and cant be removed.