If you feel that the icons are too small or too big for your liking you can very easily resize them in Windows Vista.
Just right click on an empty part of the desktop or a folder and select View. You would be able to choose between Large, Medium, and Classic icon sizes. The Classic is actually the WinXP style and is the smallest of the lot.
But what if you are the picky type and are not satisfied with any of the three available sizes? As long as you have a mouse with a scroll wheel, you can further fine-tune the size of your icons. Click anywhere on the desktop or inside a folder. Now hold the CTRL key down and scroll the mouse’s wheel up or dwon to grow or shrink the icons. It works just like you would use the scroll wheel to zoom in and out of a web page.
Remember, that this works only in Windows Vista, not in XP.
You may also want to read 6 ways to use your mouse wheen to do more in Firefox.