My advice is that you obtain at least one extra set of practice exams for each of the MCSE exams and use them as you begin studying to assess your knowledge and skills and to help you focus your subsequent efforts. Then use them again after you finish studying to assess your exam readiness; for that second application, you should seek to beat the reported "cut score" (passing score) by 10% or more, to account for the usual drop in exam scores that occurs when under the pressure of taking the real thing at the testing center. If your second application shows you're not ready yet, use it to focus further study and practice. Go for the real thing only when your score(s) is (are) at the desired level.
Remember: It's cheaper to buy an extra set of practice exams (which shouldn't cost you more than $70-80) than it is to take the exam twice (which costs an extra $125).
This was first published in June 2003