As a Windows IT professional, these are the books that I personally would keep as a reference for 2011:

Windows Internals Book 5th edition
  http://www.microsoft.com/learning/en/us/Book.aspx?ID=12069&locale=en-us
 
Windows® Sysinternals Administrator's Reference
  http://www.microsoft.com/learning/en/us/Book.aspx?ID=13439&locale=en-us

Windows PowerShell in Action, Second Edition
ISBN-10: 1935182137
ISBN-13: 978-1935182139
 
Windows PowerShell Cookbook: The Complete Guide to Scripting Microsoft's New Command Shell
ISBN-10: 0596801505
ISBN-13: 978-0596801502

 

Advanced:

Advanced Windows Debugging
http://www.advancedwindowsdebugging.com/

Advanced .Net Debugging
http://advanceddotnetdebugging.com/