This may help?
Right click the desktop and "View"
There you have 2 options for the icons. "Auto arrange... and Align.....
Also, for the size, I am guessing you have been adjusting the Size of the desktop icons through "Personalization"?
If you have not previously used Vista/7 then there is a cute new feature. Hold the Ctlr whilst scrolling with the mouse, anywhere on the desktop, and you will find the icon size is infinitely adjustable.