|Is it just your desktop icons, or has your screen resolution been decreased?|
Going from 1024x768 to 800x600, for example, will result in items on your screen appearing larger than before.
If it's just desktop icons, open up Display Properties (right-click empty area of desktop > Properties), go to the Appearance tab, click Effects button, un-check "Use Large Icons".
Apologies if I don't respond to your reply immediately. I don't check this site daily, but you're welcome to PM me as a reminder.