Or make sure you use a really strong password, if you have trouble coming out with passwords try http://pwgen-win.sourceforge.net/

If you save your wallet backups on the cloud use http://www.axantum.com/axcrypt/ to encrypt them

If you are really really really cautious encrypt your hard drive with http://www.truecrypt.org/

Ultimately you can buy a castle, hire some ninja fighters and dump some crocodiles and piranhas on the trench!