First check you are logged on as an administrator (or that your user account has administrator privilages) if you are than the next thing to check would be that on the other users do not have 'Make This Folder Private' Checked on any of their folders To check this right click on the folder and select 'Sharing and security...' as you and there for norton will not be able to acess the files. All of the above is for win xp home for Pro i think the solution is to open any folder Tools=>folder options=>view=> then enable simple folder and file sharing if none of that works then i am not sure what to do.
n.b. you can only change the make this folder private option from that users account.