Try Folder Access Folder Access Pro - Free software downloads and software reviews - CNET Download.com i'm using it since two years now and works fine. Also any third party folder protection programs will work on that OS only. So if you have two Operating systems install it on both the systems doesn't take much time.
You can use EFS in Windows XP to automatically encrypt your data when it is stored on the hard disk.
http://support.microsoft.com/kb/308989