Use NTFS security and EFS which is built into the OS providing that your partition is NTFS. Right click the file or folder and select properties, click on the security tab and set permsions for the users that you want to access the folder. If you click the advanced button which is on the general tab you can then encrypt files and folders. The administrator user has the ability to take folder ownership and is also an EFS recovery agent so you will need to protect your user password as well as the administrator password. This is more secure than any free tool you are likely to find.
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