We have a team of sales persons who travel often carrying a laptop loaded with Sales data in a SQL Server Express database. What are the options available to encrypt a SQL Server Express database?
What's your threat model? Are you trying to stop a casual thief who's stolen a laptop, or a determined hacker? Are you trying to protect just the data, or also the schema?
If you're using SQL Server Express 2005 or higher, then it supports native asymmetric encryption. But if you're trying to stop a determined hacker, then I think the best option would be to encrypt the whole disk using something like TrueCrypt, or BitLocker for Vista/Windows7.