And remember that encrypting single files might not be enough. Depending on how the software is designed, and the persistance of the thief, temp files may be available that are unencrypted. That is why whole disk encryption is stronger.

Edit: remember, even more important than encryption is physical security-if the attacker can't get the laptop, no amount of hacking/cracking technology will help them (assuming of course that you have firewall, antivirus, etc.)