Designing your miniature masterpieces is only part of your task at hand æ actually exchanging one icon for another can be a nonintuitive task for Windows users. Replacing icons for system accessories (such as the clock or notepad) requires following a different set of steps than you would to replace a shortcut to an application or a new document icon. And if you've upgraded to Windows XP, you'll have a new set of icon housekeeping rules to follow.
The Icon FAQ at iconarchive.com provides straightforward answers to basic questions about icon creation and replacement under both Macintosh and Windows.
Macintosh users will find the small but growing repository of articles at Xicons most helpful for direct assistance with updating icons under Mac OS X and customizing Apple's default system icons.
VirtualPlastic.net offers very detailed information about replacing all icon types on your Windows desktop and other interface elements.