Resize desktop icons

You may be asking the wrong question, is it only the desktop icons you want to change or is everthing too large or too small? If you have your resolution set to something that does not suit you, that may be the thing you want to change, not just the icon size. What is the brand and model of the monitor (or laptop) and what resolution do you have it set on.

For just changing icon size, if that is indeed all you want, look here http://support.microsoft.com/kb/310543 under Customize individual Windows elements by using Advanced settings