The widely used fingerprint readers and software pre-installed on laptops sold by major vendors like Dell, Sony, and at least 14 others contains a serious weakness that exposes Windows passwords in seconds. Hackers are able to quickly recover account passwords if your laptop uses software from UPEK, according to security researchers. Apparently, laptops equipped with UPEK fingerprint readers and running UPEK Protector Suite stores account passwords in Windows registry almost in plain text. This behavior is similar to when users configure a specific account to log in automatically, which is considered as a very bad practice by most IT Security Pros.
Read more here - http://arstechnica.com/security/2012/09/windows-passwords-exposed/