I recently went from 1 to 3 GoPro HD cameras that I'm using to capture and publish sailboat races with. With one camera, Windows Movie Maker worked. Now that I have 3 different pov to work with, I need a better product to edit the video with.
Here is some of the video we are playing with, all of this is single camera work.
Get Adobe Premiere Elements 9, its a really nice video editing program that goes for about $100, it has all the basic setups of premiere pro without all the complicated settings and uses (that mostly only pro film makers use). It also has 2 video channels and 2 audio channels ( i think you can increase the number of channels, not sure) which WLMM doesn't have, which means that you can add sounds in a film and a background song without them interfering and you can use the dual video channels to better organize your footage. Your computer should be able to handle it pretty well. I personally prefer Adobe products since they are very professional, efficient and if your ever stuck, their help forums are always there for support.