Windows XP (probably more after upgrade to WinXP SP2) has an unnerving habit of nagging you when it wants to reboot. Not only does it tell you that it wants/needs to reboot your computer, but it will keep opening nagging error message boxes to ask if you want to reboot.
My solution is simple: Do not answer to the question (keep the error message open), but move the small message box completely to the right side of your desktop. You’ll still have the side a small box appearing on the desktop, but it will be easy to forget about.