What is your threat model? Are you trying to stop the random thief who stole a laptop or a specific hacker? Are you trying to protect only data or a circuit?
If you are using SQL Server Express 2005 or higher, it supports native asymmetric encryption . But if you are trying to stop a particular hacker, I think the best option would be to encrypt the entire drive using something like TrueCrypt , or BitLocker for Vista / Windows7.
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