Your Hdd must be NTFS file system and you cannot use Simple File Sharing on XP Pro, on Home it a little more complicated because some of these settings have to be done in Safe mode.
For the folders you want to limit access to ,use the 'make this Folder Private tab' on User Accounts page ,right click the user icon, use this to protect you whole profile.Remember if you set restrictions 'the allow inherit permision from Parent to Prop..."tab forces these settings for everything inside that Folder or Drive. You can use this to your advantage.
Also use the Advanced permission screen on the Security tab of Properties for any item in your machine.Here you can set advanced permissions for each user at the same time.
It would be a good idea to do some reading inWindows Help or Web to make sure you have an understanding of the things you are setting.
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