I’ve been asked a few times now by friends how to change the size of desktop icons in Windows Vista. There are two ways. These methods work in Windows 7 (RC1) as well.
1. left-click an empty area of the desktop once, and while pressing down the left CTRL key on your keyboard, use the wheel on your mouse to change the size of the icons.
2. right-click an empty area of the desktop, and choose ‘view’, and choose from ‘classic’, ‘medium’, or ‘large’.