Sometimes, for various reasons, icons disappear from the Control Panel in Windows XP. This is easily remedied by downloading TweakUI and doing two things.
Open TweakUI and select the "Control Panel" menu option. Make certain that all of the options you want are selected. Once you have done this, go to the "Repair" menu option, and make sure that "Rebuild Icons" is selected. Hit "Repair Now" Your missing Control Panel icons should have reappeared.
Open TweakUI and select the "Control Panel" menu option. Make certain that all of the options you want are selected. Once you have done this, go to the "Repair" menu option, and make sure that "Rebuild Icons" is selected. Hit "Repair Now" Your missing Control Panel icons should have reappeared.