From Microsoft:
No, you can't use a password to protect files and folders in Windows. However, some programs that run on Windows allow you to protect individual files with a password [e.g. Excel]. For more information, check the Help for the program you're using.
There are other ways to protect your files and folders in Windows. You can encrypt your files using Encrypting File System (EFS), manually specify who can access the folders or files by setting permissions, or hide them. Choose your method based on how secure the folders or files need to be. Encrypting is the most secure, while hiding the folders is the least secure.
Encrypting File System (EFS) is a feature of Windows that you can use to store information on your hard disk in an encrypted format. Encryption is the strongest protection that Windows provides to help you keep your information secure.
Some key features of EFS:
- Encrypting is simple; just select a check box in the file or folder's properties to turn it on.
- You have control over who can read the files.
- Files are encrypted when you close them, but are automatically ready to use when you open them.
- If you change your mind about encrypting a file, clear the check box in the file's properties.
Note
EFS is not fully supported on Windows 7 Starter, Windows 7 Home Basic, and Windows 7 Home Premium - you can only decrypt files.
There are third party tools available to do what you want - freeware, shareware, and COTS.
Have a google!
SD