PC welt in Germany said it has discovered a major bug in Windows XP Service Pack 2 which will crack open your PC like a song thrush breaks a snail shell. The magazine said that under certain circumstances, the installation of SP2 for Windows XP "invites any Internet user to have a look around your PC".
It says that services including file and printer sharing data become visible despite the firewall being activated. The only pre-condition is that sharing for an internal network only has to be enabled and a connection made to the Internet using ISDN or dial up.
But DSL users may also be affected. PC Welt was able to open private documents on the net on PCs using XP SP2. The full article is here. The reasons for the problem, and a way to fix the problem is also published on that page.
News source: The Inquirer