Here is a nice collection of e-books for Windows XP

Windows XP for Dummies 
Windows XP for Dummies does a good job in its role as the flagship of the Dummies line, providing Windows novices with a guided introduction to Microsoft's latest and most feature-rich operating system for everyday computer users. Its treatment of computer, Windows, and Internet fundamentals is among the best on the market, and author Andy Rathbone has an appealing way of writing that's simultaneously fun and detail-rich. If you're a Windows novice--meaning you don't know how to undelete a file that's been sent to the Recycle Bin, or what a Web browser is, or what it means to "cut and paste" text--you will get a lot out of Rathbone's work.
  Microsoft Windows XP Inside Out 
Ed Bott and Carl Siechert have combined their considerable talents for producing user-level documentation in creating Microsoft Windows XP Inside Out. One of the most carefully researched books on Windows XP to date, this large volume has all the information and procedures most everyday users of the operating system will want. With its nicely formatted how-to instructions, detailed documentation of command-line commands, intelligent explanatory text, and broad scope, this book makes a great reference for a family or business that uses Windows XP extensively. Even the illustrations are more helpful than usual, largely because the publisher has gone to the trouble of annotating many of them with pointers and labels.