The icon for PerfectIt version 2 and above is removed automatically. However, for PerfectIt 1:
In Word 2000/02/03, right-click the mouse on the toolbar, then select 'Customize'. You can then drag the toolbar icon away from the toolbar and it will be deleted. Then click the 'Tools' menu and drag the 'Run PerfectIt' entry away from the menu bar in the same way.
In Word 2007/10/13, right click the mouse on the ribbon icon, then select 'delete custom command'. Make sure you click precisely on the picture in the icon or that option won't be available.