When you share your computer with others , there is always a security risk in it ,as the other user could see all your private files by means of an insecure system.
However Microsoft has released a software called windows steady state .
This is a very useful software for people who use the windows operating system .It provides various options for disabling other users from opening certain hard-disks . It can also prevent other users from accessing certain applications. This appliation is totally a freeware and only a validation is required for download .It's size is 3.38 mb.Your computer will be safe from annoying guest users thereafter.Download it from the microsoft website here.You can safely install it in your computer an ease yourself from all worries.You can manage individual users . It is highly user friendly.Make sure that you install it after logging on to your private user account.