I came across an article about how quickly (12 minutes) a base build of Windows will be attacked when left out on the internet without a firewall, security patches, etc. Recently I brought a directly connected Windows 2000 Virtual Server instance online with just a base build. I ended up walking away from my machine while the build was on the final stage of the install. I came back about an hour later to find that it had already been infected and was in the process of automatically shutting down for the third time thanks to one of the attacks. If you must run Windows make sure you wear protection.