If you want to secure that drive, I would suggest using PGP whole disk encryption. I would never use a M$ product to encrypt my data solely because they do not make their source code public.
PGP has a freeware version, but they do not allow whole disk encryption. What you could do with the free version is just create an encrypted disk volume of whatever size suits your needs and lock it up. The whole drive will not be encrypted, but any sensitive data you put in your newly created volume will be.
There are a few free programs which are decent, an example of which is
http://www.truecrypt.org/
Hope this helps