Not all hard drives or flash drives that support finger print authentication actually encrypt the data stored on them. Many biometric drives merely use the finger print to log into the hard drive, leaving the actual data unprotected.

LaCie has a very attractive portable 80GB HDD that uses biometric fingerprint authentication to login and encrypts the data with either 56-bit DES or Triple 128-bit DES. Everything USB has a full review of the Porsche designed LaCie drive on their site.
Review excerpt: "As sophisticated as bio-security may seem, the data inside is most likely not encrypted while only the fingerprints remain protected, leaving precious data vulnerable. LaCie has an answer - the Safe Mobile Hard Drive with Encryption, and the 'encryption' part is equally as crucial as the fingerprint authentication." Buy your own LaCie hard drive here.