Microsoft released a batch of security updates for Windows 2000 and Windows XP. If your system notifies you that it has downloaded new updates, be sure to install them. Or go to Windows Update and install all “critical updates.”
These updates are now a routine part of computing, just like updating virus definitions. Microsoft is switching to a monthly schedule for releasing new updates, but it’s possible to schedule the updates to occur automatically.
If your computer is left on overnight and you have a broadband connection, click on Control Panel / Automatic Updates (or Control Panel / System / Automatic Updates) and consider letting your computer automatically download and install new critical updates.