Do you want to be able to edit while viewing the 4 different angles simultaneously?
or
Do you just want to create a video where you can see all 4 angles at the same time throughout the entire video?
If it is the 1st answer. You will probably need a profesional NLE like Sony Vegas or Adobe CS3 which both have multi angle editing capabilities.
If it is the 2nd answer. All you need is an NLE that has at least 4 timelines available (such as Adobe Premier Element or Sony's consumer software). Place the videos on their own timelines, stacked on top of each other, and just resize each clip to fit in the 4 quadrants on the screen. Then just render the video.