Customizing the Windows desktop ?

I'm not sure if this is an app or a function of the OS. I would like to be able to specify a 3" by 6" box in the upper right hand corner of my desktop for Thunderbird/email. I would like the area under that to be my mp3 player app, and the areas to the left to be my 3 chat apps. I want all of theses things to be loaded and positioned whenever I start windows. Can this be done? is it an app, or a function of Windows? please give me some search terms so that I can learn more about this (if it can be done).