A security consultant, Adam Boileau, based in New Zealand has released a tool that can unlock Windows computers in seconds, via a Firewire port, without the need for a password.
With this tool, called Winlockpwn, one could "unlock locked Windows machines or login without a password ... merely by plugging in your Firewire cable and running a command".
The hack, which affects Windows XP computers but has not yet been tested with Windows Vista, was first demonstrated, at a security conference in Sydney in 2006, but Microsoft has yet to develop a fix. But now that a couple of years have passed and the issue has not resolved, Boileau, decided to release the tool on his website.