Some action could improve the security of your computer. You can for instance remove Windows™ from your computer. In this case you computer will not boot at all without the startup key and will be unusable and without any evidence on what could hold the encrypted partition. Then you can add password to BIOS and avoid boot on usb and add password to burg and gurb to avoid startup command modification.

You can also use TrueCrypt with/without inner volume to secure confidential data.

Other article from the same author are also available:

To go even further, you can apply the recommendation from the NSA:http://www.nsa.gov/ia/_files/os/redhat/rhel5-guide-i731.pdf