Go to Explorer/Tools/Folder Options/View. Scroll to the bottom and uncheck Use simple file sharing. It's checked by default. This gives you more control over security settings. You can add/remove user rights to folders and files, take ownership and work with inherited permissions. If XP Home, this can only be done in safe mode.
I set up a new computer today and can't for the life of me figure out how to give my account full permissions. This is the first time I've encountered this since I actually HAVE Admin rights according to the User Accounts (just me and the Administrator...along with default 'guest' garbage). I tried to create a new folder in one of my folders/drives and it won't let me do it....so how do I convince XP that I want FULL control over the whole shebang?
I even looked at Properties and searched for a Security tab like Help said to do and I guess the only way you see that Security tab is if you get to properties for 'individual' files...not a complete drive...so that isn't going to help me any.