I've stuck with XP until they make a better system (from my point of view, anyway). Haven't been real impressed with the last three, so am still waiting.
Once you trim XP down and get rid of all the garbage and eye candy, it's a very functional, stable, and easy system to use.
I use a small freeware programme called MW Snap. Once minimised in the bottom toolbar, a right click on the icon opens a menu with a lot of options - fixed size rectangle, any selected area, full screen, window etc. It can then be saved in a choice file types and resolution. It also has some other editing tools I've never used. I think there's others around, but this one is easy.
Cheers, Willie.