So I've decided to get my feet wet with Microsoft after tackling the standard three of CompTIA (Sec, Net, and A+). I want to tackle a Microsoft exam and the one I'm most comfortable with is 70-270 given my XP experience (although I've used Vista and 7 extensively as well). So I guess my question is, where should I start with Microsoft? I'm looking to maybe go for my MCSE, so I figured the OS was a good place to start.
Does anyone have any tips for which certification to start with, or if its 70-270, which materials to study with? Currently I have the Sybex book: 
Amazon.com: MCSA/MCSE Windows XP Professional Study Guide (70-270), 3rd Ed. (9780782144123): Lisa Donald, James Chellis: Books