This attack is basically the same as SQL Slammer. Except it uses a buffer overflow in DCOM on netbios/samba ports rather than a buffer overflow in SQL Server on port 1434.
Anyone with half a brain would never have a SQL server open to the internet like that, but look at my sig.....
Having netbios/samba ports open to the internet with a Windows machine is also incredibly stupid for reasons other than this attack, but I'd wager the majority of home Windows users currently have such a configuration.
If turning on Windows messenger service causes you to receive stupid popups without any browser running, then you are open to this attack unless patched (or better yet) you go and get a firewall in place. If you have a firewall that you don't leave completely open, you should be immune to both this and those stupid messenger popups from the internet, although someone could theoretically fire off the attack on your LAN, particularly someone attaching a laptop that was previously in hibernate mode.