Not sure if it will work with an uncompressed folder.
To protect files in a zipped compressed folder with a password
Open My Computer, and then locate the compressed folder.
Double-click the compressed folder.
On the File menu, click Add a Password.
In the Password box, type a password.
In the Confirm Password box, type the password again.
To open My Computer, click Start, and then click My Computer.
Passwords are case sensitive.
You can identify compressed folders by the zipper on the folder icon.
When you extract an password protected file, the extracted file is no longer protected.