Microsoft released a security advisory on a vulnerability in the Remote  Desktop Protocol (RDP) a little while back. Their advisory basically stated that it's possible to remotely crash a machine via the RDP protocol. Fortunately for most users RDP is not enabled by default. However, if you're running Windows XP Media Center Edition, it *IS* enabled.

Since then, a number of scans for the RDP port have been detected. It's unclear if those scans are designed to try and crash machines or if someone's figured out how to exploit RDP to allow them to take control of the machines they can contact.

Once again, this reinforces the need to have some form of firewall between a Windows computer and the Internet. If you don't have a router providing protection, then you should have a personal firewall! Microsoft recommend blocking TCP port 3389 at the firewall, and disabling Terminal Services and the Remote Desktop feature.