All administrator accounts are equivalent. To control file and folder access on a single machine, you need to set permissions on the files and folders. I don't remember if the Home Edition of XP exposes the user interface required to do this, but all the infrastructure beneath is there, so if you have a tool to manipulate permissions, you can do whatever you want. Permissions must be changed with care or you can lock yourself out of things that might be awkward to recover. Windows 7 sets permissions by default that isolate users from each other and allow only administrator access to certain files and folders. This is true even in the Home Edition (or Premium Home Edition, or whatever Microsoft calls it these days).