first, if you want to set permissions on a file or folder, your drive must be formated in NTFS. second, inorder to see the 'security' tab, when you check the "properties" of said file or folder.. you have to have unchecked the box 'use simple file sharing (recommended)'. where do you find this box ? launch an explorer box, then click on 'tools', then 'folder options', then 'view', then scrool down to the bottom of the 'advanced settings:' section. it is at the bottom of the page. unchecking this will now give you a 'security' tab when you select the properties of a file or folder. so do that on a file or folder, then click on the security tab, then customize the options you want everyone to have (read, write, ect...). you can also strip away all access, if you are an admin. is all assumes you are an admin, not sure if you can do any of this if you are not.