Create a partition and encrypt it with BitLocker (built into Windows). Put your local Dropbox there. Pretty straightforward. The only annoying bit is Dropbox wi

Create a partition and encrypt it with BitLocker (built into Windows). Put your local Dropbox there. Pretty straightforward. The only annoying bit is Dropbox will fail to initialize upon windows start when it can't find the folder because the encrypted partition is inaccessible until you unlock it.