The practice questions included on the CD-ROM with the book "MCSE Training
Kit (Exam 70-270): Windows® XP Professional" as well as the questions at the
end of each chapter comes to mind.
http://www.microsoft.com/mspress/books/5398.aspx
Doing a Google search for Exam 70-270 practice questions results in alot of
pay to download and some sites that have a small sampling of questions.
I don't know what your desktop client certification path desires are, but
you might also consider either CompTIA A+ or the more modern Windows desktop
client "Vista". That being said, I know there are alot of Windows XP desktop
clients out there that still need support.
