What is your primary concern with laptop theft -- data deprivation or data theft? That is, are you screwed six ways to Sunday because a thief now has access to client photos and information or because you only have one copy of that information and it's on the computer?
If it's the latter, ALWAYS BACK UP! You should never have only one copy of an image anywhere, ever. When you do a photoshoot, if you dump your CF to your laptop, that CF should not be erased until you've mirrored those images onto another drive back at your studio. Always two copies at all times.
If it's the former, I'd reccomend a program called "Truecrypt". It's free and open source. If you select the "full system encryption" option, this program will force a password entry at system start. Without this password, the system will essentially be a brick; the entire drive is encrypted with strong cryptography and the contents of the drive are completely irretrievable. When my laptop boots, all that is displayed is a message that says "If found, call xxx-xxx-xxxx". Only by entering in my password will the system boot.
This makes the laptop harder to fence. Most people who steal laptops are doing it to fence at a pawnshop or somesuch for quick drug money. Rarely will a pawn owner accept a laptop if it boots to a screen that the pawner can't figure out how to get past. Rarely will a druggie have any idea how to reformat a hard drive and reload all software (nor will they have the motivation to do so).
Lastly, insure your laptop. You can usually get a rider on your homeowners/renters insurance for this. If it is stolen, get compensated and get a new one.