Access control.  

Ready, Set, Control. Another way to keep prying eyes away from your files is to use access control. In Win98, you have a choice of two types of access control: share level and user level .
Share-level access control lets you restrict who can use resources, such as folders, drives, and printers, by assigning a password to each one. Anyone who knows the password for a resource can use it, making it easy to share resources with a number of people without a lot of fuss. However, this benefit is also the featureís weakness. What happens if a password falls into the wrong hands or is more widely distributed than you intended?

In contrast, you set user-level access control by compiling a list of people or workgroups who can use the file or folder. Because the users are already on a master list (which is usually maintained by a network administrator), they donít need a specific password to use the resource because their presence on the list has already given them permission.

Access Manager - More info

     If the above options do not provide enough security for you, download Access manager for Windows.

Access manager provides much more security than standard ways in Windows.

More info

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