This is one of the main security issues you might have. Any breach in your private files is a huge problem. So there is a software for it from a reputable company. Its from HP. So lets talk about the HP Trust Circles.
HP Trust Circles Features
This is a software which is easy to install. The authentication is also easy. The security is reduced if you do use a weak windows password. So use a good windows password.
The software transparently does encrypt the files in the specified folders. There is no provision to enforce strong password which was required. The encryption stays as it is when the files are transferred. This software has a seamless files access.
You have the authority to provide anybody access to a particular file. So be tension free if the file even gets into hands of a wrong person. He/she will not be able to access the file as it will highly encrypted by the HP trust circle. A must use software so as to prevent access to anauthorized parties.